The scale of the challenge is sobering. DSRCT is an aggressive soft tissue sarcoma in which nests of small round tumour cells are embedded in a dense, fibrous stroma, the very desmoplastic tissue that gives the disease its name. In 90 per cent of patients, tumours have already spread diffusely throughout the abdominal cavity by the time of diagnosis, and half have metastasised beyond the peritoneum to the liver, lungs, lymph nodes or bones. Eighty per cent of cases occur in post-pubertal males, with a peak incidence between the ages of 20 and 24. Current treatment, a punishing combination of intensive multi-agent chemotherapy, cytoreductive surgery and whole-abdomen radiotherapy, has produced no meaningful improvement in survival in 30 years. Even after complete surgical resection, some studies report recurrence or progression in 84 per cent of patients, and up to 70 per cent of surgically treated patients require further procedures.

At the molecular level, DSRCT is a paradox. It is a genomically ‘quiet’ cancer, meaning it carries remarkably few mutations beyond its defining event: a reciprocal translocation between chromosomes 11 and 22 that fuses the EWSR1 gene to WT1, producing an abnormal transcription factor found exclusively in tumour cells. This fusion protein, present in every DSRCT cell, combines the transactivation domain of EWSR1 with the DNA-binding domain of WT1, rewiring gene expression across the genome. Laboratory studies have shown that suppressing the fusion protein halts tumour cell growth entirely, triggering cell-cycle arrest and shrinking xenograft tumours in mice. The workshop participants unanimously ranked EWSR1::WT1 as the highest-priority target, but hitting it directly is extraordinarily difficult because the protein is structurally disordered and buried in the cell nucleus.

One of the most exciting strategies discussed targets the fusion protein through the immune system. The chromosomal breakpoint creates a unique junctional amino acid sequence, a neoantigen that exists only in tumour cells and never in healthy tissue. Using mass spectrometry of HLA molecules, researchers confirmed that this neopeptide is displayed on the cell surface by two globally common HLA variants, HLA-A03 and HLA-A11. Engineered T-cell receptors designed to recognise this peptide have shown complete and durable responses in animal models. The catch is HLA restriction: only around 32 per cent of DSRCT patients worldwide carry the required tissue types, though efforts are under way to broaden coverage, and future iterations may be armoured with immune-stimulating cytokines such as interleukin-18. A parallel technology, peptide-centric chimeric antigen receptors, which are not limited by HLA type, is earlier in development but could eventually offer a wider route to the same target.

Indirect approaches to disabling the fusion protein are already in the clinic. Trabectedin and its analogue lurbinectedin are small molecules that bind the DNA minor groove and disrupt the fusion protein’s activity, and lurbinectedin is now being tested in DSRCT both as a monotherapy and in combination with irinotecan. Beyond the fusion itself, the workshop identified several cell-surface proteins as promising targets, including LRRC15, the somatostatin receptors SSTR3 and SSTR5, NECTIN4, STEAP1 and mesothelin. Each is attractive in principle, but the participants stressed that proteomic validation in DSRCT tissue remains thin. A single case report of a patient with atypical DSRCT achieving a 23-month response to the NECTIN4-targeting antibody-drug conjugate enfortumab vedotin hints at what may be possible, but the panel cautioned that far more expression data are needed before such drugs can be justified for routine investigation.

Some of the most encouraging clinical signals come from drugs already approved for other cancers. Trastuzumab deruxtecan, an antibody-drug conjugate linking a HER2-targeting antibody to a topoisomerase I inhibitor, produced partial responses in nine of 17 DSRCT patients with measurable disease in a single-centre off-label study, with a further eight achieving stable disease. Strikingly, response did not correlate with HER2 expression levels, and preclinical work suggests the drug is active even at low HER2 abundance. Those results have propelled a biomarker-agnostic trial through the Children’s Oncology Group. Other trials now under way include an antibody-drug conjugate against claudin-6, the NTRK3 inhibitor repotrectinib combined with chemotherapy, and the somatostatin analogue pasireotide as maintenance therapy for tumours expressing SSTR2, 3 or 5.

The workshop also prioritised existing clinical assets that could be redeployed. B7-H3, a cell-surface protein expressed in up to 96 per cent of DSRCT tumours but minimally in healthy tissue, was rated a very high priority, with an antibody-drug conjugate carrying a topoisomerase 1 payload considered the optimal modality. Inhibitors of the DNA damage response also ranked highly, because DSRCT cells show high levels of replication stress; a phase I trial of the CHK1/2 inhibitor prexasertib with irinotecan produced partial responses in six of 19 patients. Androgen receptor signalling emerged as potentially ‘low-hanging fruit’, given that hundreds of AR-targeted drugs already exist for prostate cancer and that AR is highly expressed in many DSRCT cases, particularly in males. FGFR4, a direct transcriptional target of the fusion protein, and STEAP1 round out the shortlist, with cell-surface approaches such as CAR T-cells and antibody-drug conjugates favoured over small-molecule inhibitors.

Yet the workshop was candid about the barriers that have kept DSRCT patients waiting. With so few patients, pharmaceutical companies have little financial incentive to run trials, and regulatory frameworks designed for common adult cancers fit poorly. The participants proposed three complementary solutions: international platform trials such as the OCTOPUS master protocol for non-rhabdomyosarcoma soft tissue sarcomas, which can test multiple agents simultaneously and adapt as data emerge; the systematic collection of high-quality off-label and real-world evidence, as demonstrated by the trastuzumab deruxtecan experience; and the inclusion of DSRCT patients in adult trials of relevant targets, for example by adding signal-seeking DSRCT cohorts to prostate cancer studies of androgen receptor inhibitors. Trials in the setting of minimal residual disease, where the chance of altering the disease’s natural history may be greatest, were also flagged as a priority, alongside better tools to detect and characterise the residual cells that seed relapse.

For a disease that has defied progress for a generation, the workshop’s message is one of cautious momentum. The biology of DSRCT, once an impenetrable black box, now offers a defined driver, a tumour-specific neoantigen, a growing list of surface targets and a pipeline of drugs, many already tested in humans, that could be redirected toward these patients. The participants concluded that progress will come from a dual strategy: developing entirely new agents against the EWSR1::WT1 fusion while simultaneously evaluating existing therapeutics in well-designed, internationally harmonised trials that enrol children, adolescents and adults together. If the roadmap is followed, the first generation of DSRCT patients with genuine targeted options may not be far away, turning one of oncology’s most neglected diagnoses into a test case for how science can serve the rarest of the rare.

Subject of Research: Therapeutic target prioritisation and clinical trial strategy for desmoplastic small round cell tumour

Article Title: Paediatric therapeutic development workshop on desmoplastic small round cell tumours

Article References: Baxter, J. S., Molenaar, J. J., Agrawal, A., Amaral, A. T., Blanc, P., Bowdidge, N., Bowdidge, R., Brennan, B., Casanova, M., da Silva Moura, D., Daems, S., Danielson, L., English, S., Grohar, P., Halliwell, E., Huang, P., Kearns, P., Klebanoff, C. A., Klaourakis, K., … Daems, S. (2026). Paediatric therapeutic development workshop on desmoplastic small round cell tumours. British Journal of Cancer. https://doi.org/10.1038/s41416-026-03631-7

Image Credits: AI Generated

DOI: 10.1038/s41416-026-03631-7

Keywords: DSRCT, EWSR1::WT1 fusion, paediatric oncology, sarcoma, T-cell receptor therapy, antibody-drug conjugates, B7-H3, androgen receptor, DNA damage response, rare cancers, drug development, clinical trials

NCCN Guidelines occupy a distinctive position in modern oncology. They are compiled by more than 60 expert panels drawing on more than 2,000 interdisciplinary specialists from the network’s 34 member institutions, working alongside patient advocates, and they are updated continuously rather than on a fixed revision schedule. Independent studies have found that care delivered in concordance with these recommendations is associated with longer survival, better outcomes, and lower costs across a range of cancer types. The guidelines function as a roadmap for clinicians making complex treatment decisions, establishing guardrails against both overtreatment, which exposes children to unnecessary toxicity, and undertreatment, which can compromise the chance of cure. For a rare pediatric cancer, where an individual oncologist may encounter only a handful of cases across an entire career, that kind of standardized expert consensus can be transformative.

The clinical picture of Ewing sarcoma helps explain why dedicated pediatric guidance is so important. The disease typically strikes teenagers between the ages of 15 and 19, a developmental window in which patients are forging their identities and their sense of independence. It often announces itself as severe and persistent pain or swelling in the limbs or pelvis, symptoms that overlap substantially with far more benign adolescent complaints such as sports injuries and growing pains. Because of that overlap, x-rays serve as a key first step in the diagnostic process, allowing physicians to identify suspicious bone lesions before proceeding to more definitive imaging and biopsy. The guidelines therefore address not only treatment but the diagnostic pathway that determines how quickly a young patient reaches specialist care.

Survival statistics underscore the stakes. When Ewing sarcoma is diagnosed at an early, localized stage, the five-year survival rate stands at 81 percent, a figure that reflects decades of progress in multimodal therapy combining chemotherapy, surgery, and radiation. When the disease has already spread to distant sites by the time of diagnosis, however, that rate falls to 41 percent. The steep drop-off between localized and metastatic disease illustrates both the progress that has been achieved and the considerable distance that remains. It also highlights the importance of risk stratification, the process of sorting patients by the biological and clinical features of their tumor so that therapy intensity can be matched to the true severity of disease, a topic on which Dr. Leavey noted there have been significant improvements in recent years.

Patrick Leavey, MD, of UT Southwestern Simmons Comprehensive Cancer Center, who chairs the NCCN Guidelines Panel for Pediatric Bone Sarcoma, emphasized the particular vulnerabilities of the adolescent patient population the guidelines are designed to serve. Intensive cancer treatment, he explained, can drain a teenager’s energy and disrupt their developing sense of autonomy at precisely the moment when they are striving for independence. The guidelines, in his view, serve a reassurance function as well as a clinical one, ensuring that young patients know they have a knowledgeable team ready to support them through a regimen that will test them physically and emotionally. That dual purpose, technical precision paired with developmental sensitivity, distinguishes pediatric oncology guidance from its adult counterparts.

The patient advocate perspective on the panel carries equal weight in shaping the document. Paula Head, who served as a caregiver for her own daughter, described the guidelines as clear, accurate medical roadmaps that reduce anxiety and build confidence in the care a child is receiving. Her advocacy was driven by a conviction that pediatric cancers and their treatments differ fundamentally from those of adults, and that families deserve recommendations written specifically for children rather than adapted from adult protocols. Reflecting on the toll the disease takes on young people, she offered a simple measure of its impact: whether the number of children affected is one or 101, whatever that number is, it is too many.

One of the thorniest challenges in advancing care for Ewing sarcoma is its sheer rarity. Clinical trials, the engine of therapeutic progress in oncology, depend on enrolling enough patients to detect meaningful differences between treatment approaches. A cancer this uncommon makes that arithmetic difficult, and Dr. Leavey pointed to clinical trials as essential to overcoming the stagnation that rarity can impose. Cooperative group trials that span multiple countries and institutions have historically been the mechanism by which pediatric sarcoma outcomes have improved, and the new guidelines are expected to reinforce the trial infrastructure by standardizing the baseline care against which experimental approaches are compared. Recent gains in risk stratification, which allow clinicians to identify which patients need the most aggressive therapy and which might be spared its long-term consequences, represent the kind of progress that careful, coordinated data collection makes possible.

The publication of pediatric bone sarcoma guidance completes a deliberate expansion of NCCN’s pediatric portfolio. Children are not simply small adults: their cancers arise from different biological processes, their bodies respond differently to chemotherapy and radiation, and their long-term survivorship needs, spanning decades of growth and development, demand a distinct framework. By issuing disease-specific pediatric guidelines, the network gives community oncologists and pediatricians outside major cancer centers a direct line to the consensus of the most experienced specialists, potentially shortening the time between diagnosis and appropriate referral. For families, the existence of a free, authoritative reference can convert an overwhelming and opaque journey into a navigable one.

Access is a central part of the NCCN model. All of the guidelines are available free of charge for non-commercial use at NCCN.org and through the Virtual Library of NCCN Guidelines App, and most can now be explored digitally through the NCCN Guidelines Navigator, which allows clinicians to search content interactively rather than paging through traditional PDF documents. Free website registration is required to access the clinical content. That open-access philosophy reflects the network’s mission as a not-for-profit alliance of leading cancer centers devoted to patient care, research, and education, and it ensures that the new pediatric bone sarcoma recommendations can reach practitioners anywhere in the world, including regions where specialized sarcoma expertise is scarce.

For the teenagers and families facing Ewing sarcoma, the arrival of dedicated guidelines is unlikely to change the biology of the disease, but it may change the experience of confronting it. Standardized recommendations mean that a child diagnosed in a community hospital can receive care aligned with the same evidence and expert judgment that governs treatment at the most advanced cancer centers. They mean that the questions families ask, about which therapies to pursue, which trials to consider, and what supportive care to expect, can be answered with reference to a shared, transparent document. And they signal to the research community that this rare and formidable cancer now has a formal place in the framework of modern oncology, a foundation on which the next generation of therapeutic advances can be built.

Subject of Research: First NCCN clinical practice guidelines for pediatric Ewing sarcoma and other bone sarcomas in children and adolescents

Article Title: A formidable type of childhood cancer gets added to highly regarded library of treatment recommendations

Article References: A formidable type of childhood cancer gets added to highly regarded library of treatment recommendations. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Ewing sarcoma, NCCN Guidelines, pediatric oncology, bone sarcoma, clinical practice guidelines, childhood cancer, risk stratification, clinical trials, adolescent health, cancer survival rates, treatment recommendations, rare cancers

Now a team of researchers from Meenakshi Medical College Hospital and Research Institute in Tamil Nadu, India, has published a formal commentary in the same journal challenging that interpretation. In a Matters Arising contribution, R. Saravanan, Paramanantham Madhavan, R. Sivayogana, and K. Anusha do not dispute the value of the underlying registry analysis, which they describe as an important framework for evaluating rare cancers using population-level data. Instead, they raise two methodological concerns that, if correct, could substantially alter how the German findings should be read. The first concerns whether the apparent rise in multivisceral resection reflects a real change in surgical practice or simply an improvement in how operations were documented and coded over time. The second concerns the handling of missing data on tumor grade and metastatic status, variables that were absent in a large fraction of cases yet still used to stratify survival analyses. Both concerns strike at the heart of a growing movement in oncology: the use of registry data to draw clinical conclusions about diseases too rare for randomized trials.

The argument about coding is technically subtle but conceptually compelling. The German analysis of organ resections relied on a subset of only 1,318 patients with codeable resection procedures, a considerably smaller group than the full surgical cohort, and it depended entirely on whether the Operationen- und Prozedurenschlüssel, the German procedure coding system, captured a code for every organ removed during each operation. The commentary points out that the original paper itself acknowledged a parallel phenomenon: the rise in annual case numbers over the same period was attributed to improving case ascertainment and documentation completeness following the 2014 legal framework for cancer registration, not to a true increase in disease incidence. If overall case documentation improved across two decades, the Indian authors argue, it is plausible and untested that procedure-level documentation improved as well. Under that scenario, earlier multivisceral resections may have been underdocumented, with only the single most prominent procedure code recorded, while later cases benefited from more complete coding that captured every organ removed in the same operation. Part or all of the observed temporal trend would then reflect better paperwork rather than bolder surgery.

The distinction is far more than methodological tidiness. If the trend is substantially a documentation artifact, the commentary notes, then the implicit message to clinicians and registry stewards, that German surgical practice has progressively converged on international multivisceral resection guidelines for liposarcoma, would be overstated. The more accurate takeaway would concern the maturation of registry coding rather than the maturation of surgical decision-making. The authors propose a concrete diagnostic test: reporting the proportion of surgical cases with at least one codeable resection procedure by diagnosis year, alongside the existing organ-count trend, would allow readers to judge whether the apparent rise in multivisceral resection tracks improving procedure documentation or represents an independent change in clinical practice. If the two curves move together, the documentation explanation gains weight; if they diverge, the practice-change interpretation becomes more credible. Such a check costs nothing beyond additional analysis of data already in hand, which is precisely why the commentary frames its absence as a missed opportunity.

The second major concern involves missing data in the survival analyses. According to the commentary, grading information was missing in twenty-four percent of cases, and distant metastasis status was missing in fifty-five percent, yet both variables were used to stratify the survival analyses and the primary treatment description without any sensitivity analysis addressing whether the missingness was informative. This matters because of a well-known statistical hazard: complete-case analysis, in which patients lacking a given variable are simply excluded, produces unbiased results only if the missing data occur randomly. If, as the original paper’s own discussion suggests, earlier-era cases suffered from less complete documentation, then those cases may be disproportionately represented among patients with missing grading or staging information. The Kaplan-Meier survival curves and treatment-pattern tables restricted to complete cases would then systematically overrepresent more recent, better-documented tumors, which may differ from the excluded cases in surgical approach, tumor biology ascertainment, or case mix. The resulting curves could paint a rosier or otherwise distorted picture of outcomes across the full registry cohort.

The commentary applies this concern specifically to the Kaplan-Meier estimates stratified by grade, which were calculated only among the roughly three-quarters of cases with recorded grading. No comparison of baseline characteristics between graded and ungraded cases was provided to establish that the two groups were otherwise similar. The authors suggest a remedy that mirrors their proposal on procedure coding: reporting whether missingness in grading and metastasis status varies systematically by diagnosis year, and providing a basic comparison of age, sex, and histology distribution between complete and incomplete cases. Such comparisons would allow readers to judge whether the survival and treatment-pattern findings generalize to the full registry cohort or are specific to the more thoroughly documented subset. The commentary also notes an internal inconsistency in the original paper’s logic: the study elsewhere treats improving documentation completeness as a plausible explanation for other temporal patterns in the dataset, yet does not extend that same reasoning to the grading and staging variables underlying the survival analysis.

What makes this exchange notable is its constructive tone and its broader relevance. The Indian authors explicitly state that neither concern displaces the substantial contribution of the German study, which established a reproducible, histology- and location-specific framework for extracting a rare tumor cohort from national registry data. They call that framework a genuinely useful methodological template for future rare-cancer registry research well beyond retroperitoneal sarcoma. The stakes they identify are correspondingly high: distinguishing genuine practice change from improved documentation completeness, and characterizing whether missing data correlate with diagnosis era, would allow clinicians and health-policy readers to rely on reported trends as evidence of evolving surgical practice with greater confidence, rather than treating documentation artifacts as clinical signals. In an era when health systems increasingly mine administrative and registry data to guide cancer care, the commentary is a reminder that the quality of the data pipeline can be as consequential as the quality of the medicine it records.

The technical issues at play are familiar to epidemiologists but deserve wider understanding. Procedure coding systems like the German OPS are designed for billing and administration, not research, and their granularity depends on local coding habits, staffing, and evolving regulations. Studies of complex surgical specimens in other fields have documented substantial variability in how thoroughly multi-organ procedures are captured in coded records, and the commentary cites work on procedural terminology optimization in genitourinary surgery as an illustration. Similarly, the problem of informative missingness in registry-based survival analysis has prompted a growing literature on imputation techniques for Kaplan-Meier estimation, which the commentary references. Neither problem is unique to the German study; both are endemic to registry research. The commentary’s contribution is to show how these general hazards map onto the specific claims of a high-profile national analysis, and to propose analyses that would resolve the ambiguity without requiring new data collection.

For patients with retroperitoneal sarcoma, the practical implications are indirect but real. Multivisceral resection is the single most important determinant of long-term survival in this disease, and international guidelines recommend aggressive compartmental surgery for liposarcoma whenever feasible. If German practice has genuinely converged on those guidelines over two decades, that is encouraging news for the roughly one in a hundred thousand people diagnosed each year. If instead the trend partly reflects coding maturation, the appropriate response is not complacency about surgery but investment in registry quality, so that future analyses can distinguish the two. The commentary, published open access in October 2026, ultimately asks for methodological consistency: the same skepticism about documentation quality that the original authors applied to case counts should be applied to procedure codes, tumor grades, and staging data. Whether the German group responds with the requested sensitivity analyses will determine how confidently the oncology community can cite this study as evidence that surgical practice, and not merely surgical record-keeping, has changed.

Subject of Research: Methodological evaluation of German cancer registry data on retroperitoneal sarcoma treatment trends

Article Title: Comment on “Treatment of retroperitoneal sarcoma in Germany between 2000 and 2022: a retrospective analysis from the German Cancer Registry Group”

Article References: Saravanan, R., Madhavan, P., Sivayogana, R., & Anusha, K. (2026). Comment on “Treatment of retroperitoneal sarcoma in Germany between 2000 and 2022: a retrospective analysis from the German Cancer Registry Group”. Journal of Cancer Research and Clinical Oncology, 152(10), Article 189. https://doi.org/10.1007/s00432-026-06591-w

Image Credits: AI Generated

DOI: 10.1007/s00432-026-06591-w

Keywords: retroperitoneal sarcoma, cancer registry, multivisceral resection, registry completeness, missing data, survival analysis, surgical oncology, liposarcoma, rare cancers, clinical epidemiology, procedure coding, Germany

The biological logic behind MSI-H/dMMR immunotherapy is the strongest in the field. When the mismatch repair machinery fails, cells accumulate insertion and deletion mutations that generate frameshift neoantigens, provoking a characteristic immune state: dense CD8-positive T-cell infiltration, heightened interferon signalling and adaptive upregulation of PD-1. Crucially, this immune phenotype is conserved across many tumour types, which is why pembrolizumab produced durable responses in roughly one-third of patients across more than 25 malignancies in the KEYNOTE-158 trial, with a median duration of response of 63.2 months. The paradigm extended beyond a single drug when the FDA granted accelerated approval to dostarlimab for previously treated recurrent or advanced dMMR solid tumours in 2021, supported by the GARNET study, in which the objective response rate reached 44 percent with responses lasting a median of 27.7 months. This, the authors argue, is what a genuine tumour-agnostic biomarker looks like: a shared, immune-sensitive biological state rather than a shared mutation.

Tumour mutational burden tells the opposite story. The premise was seductive: more mutations should yield more neoantigens and greater sensitivity to checkpoint blockade. But the pan-cancer experience exposed a fundamental flaw in that reasoning. A threshold of 10 mutations per megabase conflates biologically disparate cancers with different mutational processes, neoantigen quality, antigen-presentation machinery and immune microenvironments. TMB quantifies mutation burden while ignoring immunogenicity, T-cell infiltration and immune exclusion, all of which determine clinical response. In KEYNOTE-158, 102 patients with TMB-high tumours across ten histologies achieved an objective response rate of 29 percent, which was enough for the FDA’s 2020 accelerated approval of pembrolizumab for TMB-high solid tumours without satisfactory alternatives. Real-world datasets, however, show substantial heterogeneity by tumour type, with predictive value remaining strong mainly in cancers already characterised by immune infiltration. The immune ecosystem of a pancreatic adenocarcinoma differs fundamentally from that of a melanoma, regardless of whether a shared biomarker is present.

The review proposes that immunotherapy biomarkers be understood as layered rather than binary, spanning four domains. Tumour-intrinsic markers include MSI-H/dMMR, TMB, POLE and POLD1 mutations, viral antigens, DNA damage repair defects, mutational signatures and HLA loss. Immune microenvironment markers include PD-L1 expression, tumour-infiltrating lymphocytes, CD8 T-cell localisation, interferon signalling, myeloid infiltration and tertiary lymphoid structures. Host and systemic markers encompass immune fitness, microbiome composition, corticosteroid exposure and autoimmune risk, while dynamic markers include circulating tumour DNA kinetics, early radiographic patterns and immune-related toxicity. This layered model explains why single biomarkers perform inconsistently in tumour-agnostic practice. A high TMB result, for example, may be far less informative when it reflects treatment-induced hypermutation, such as temozolomide-associated hypermutation in recurrent glioma, rather than a clonal, endogenous immune-sensitive state.

The validation gap between candidate biomarkers is stark. PD-L1 protein expression has established tumour-specific assays and clinical utility, but its predictive value depends on the assay clone, scoring method, threshold and tumour lineage, and no PD-L1-expression-defined pan-cancer indication exists. PD-L1 gene amplification is rarer still, found in roughly 0.7 percent of tumours across more than 100 histologies in one pan-cancer series, and retrospective data suggest greater checkpoint inhibitor activity in amplified tumours, but no validated selection standard has emerged. Pathogenic POLE and POLD1 proofreading defects produce ultramutated, immunogenic phenotypes and correlate with checkpoint inhibitor efficacy, yet no regulatory indication rests on them alone, and the evidence is strongest in colorectal and endometrial cancers. Viral association, T-cell-inflamed gene signatures and tertiary lymphoid structures all carry biological plausibility and supportive evidence, but none constitutes a validated tumour-agnostic biomarker suitable for standalone prescribing.

Rare cancers expose the paradigm’s sharpest dilemma. Many are systematically excluded from pivotal trials yet demonstrate immunotherapy sensitivity without validated predictive biomarkers, as seen in Merkel cell carcinoma, alveolar soft-part sarcoma, thymic carcinoma and selected neuroendocrine subtypes. The SWOG S1609 DART trial, a phase 2 basket study of ipilimumab plus nivolumab across 53 rare cancer cohorts, enrolled 798 patients and confirmed responses in 24 of 53 cohorts, with an overall response rate of 13 percent and durable benefit in angiosarcoma, neuroendocrine tumours and rare gynaecological malignancies. The Australian MoST-CIRCUIT trial reported an objective response rate of 54 percent in advanced ovarian and endometrial clear cell cancers, most of which were mismatch repair-proficient and low TMB, and 63 percent in non-colorectal dMMR/MSI-H cancers across 17 tumour types. These results reveal immune-sensitive cohorts while leaving clinicians without biomarkers capable of identifying individual responders.

This is what the authors call the clinical grey zone: a patient with a rare cancer, exhausted standard options, emerging evidence of immunotherapy activity, no validated biomarker, no reimbursed molecular test and no feasible trial. A strictly biomarker-defined access model may be too restrictive, but unrestricted prescribing risks unwarranted toxicity, false hope and low-value care. The authors propose a pragmatic framework weighing four linked domains: strength of clinical evidence, biological and biomarker evidence within tumour-lineage context, competing treatment options, and patient-specific benefit-risk. Treatment can be recommended when convincing evidence or a validated immune-sensitive state exists and no superior option is available; considered with multidisciplinary review when uncertainty remains; and avoided outside a trial when evidence is absent, a superior therapy exists, or toxicity risk outweighs plausible benefit. The framework is deliberately not a numerical score, because strong evidence in one domain may override uncertainty in another.

Australia has become the world’s most consequential test case. In 2026, the Pharmaceutical Benefits Scheme consolidated and expanded public reimbursement of ipilimumab plus nivolumab and pembrolizumab for eligible patients with advanced or metastatic cancers considered immunotherapy-sensitive, including rare and uncommon cancers lacking conventional trial data. The listing, described as a world first and the product of partnership between government, industry, clinicians and patient advocates, includes shared costs between government and sponsor and a reassessment after three years. Critically, the reimbursement change did not create a corresponding tumour-agnostic regulatory indication, and the listing does not require a positive biomarker. Because broad pan-cancer next-generation sequencing is not universally funded in Australia, the country may be the first to fund pan-cancer immunotherapy without simultaneously funding the biomarker testing infrastructure needed to deploy it, transferring substantial selection responsibility to treating clinicians.

The economics of immunotherapy are also shifting. Annual treatment costs for PD-1 and PD-L1 inhibitors in the United States commonly exceed US$100,000 per patient, and multiple cost-effectiveness analyses have questioned the sustainability of broad population-level use at originator prices. Competition, biosimilar development and alternative procurement models may progressively reduce price as the sole determinant of access. As financial barriers ease, the question of appropriate use intensifies: severe immune-related adverse events occur in 15 to 20 percent of patients receiving checkpoint inhibitors, with fatal outcomes in 0.3 to 1.2 percent of cases. Reimbursement policy, the authors argue, cannot be considered independently of patient selection, and structured decision frameworks become the mechanism for translating genomic and immunologic data into responsible clinical guidance.

The lessons extend beyond checkpoint inhibitors to emerging pan-tumour platforms, including antibody-drug conjugates, bispecific antibodies and cellular therapies. Shared target expression among tumour types does not necessarily define a conserved therapeutic vulnerability: for antibody-drug conjugates, target density, internalisation kinetics, spatial heterogeneity, payload sensitivity and tumour lineage all influence efficacy despite expression of the same antigen. The review’s conclusion is measured but pointed. Tumour-agnostic immunotherapy has not made tumour type obsolete; it has shown that in selected settings biology can be more clinically informative than anatomy. Whether Australia’s experiment succeeds will depend on four prerequisites: funded molecular testing, expert decision support, prospective registries capturing outcomes and toxicity, and mechanisms for reassessment. Without those safeguards, the authors warn, the model risks both waste and harm, funding the drug before funding the pathway that decides who should receive it.

Subject of Research: Tumour-agnostic immunotherapy biomarkers and implementation of pan-cancer checkpoint inhibitor reimbursement

Article Title: Tumour-agnostic immunotherapy: aligning biological rationale, biomarker precision, and real-world implementation

Article References: Liu, J., Beal, J., Coleman, N., Lynam, J., & Subbiah, V. (2026). Tumour-agnostic immunotherapy: aligning biological rationale, biomarker precision, and real-world implementation. eClinicalMedicine, 100, Article 104211. https://doi.org/10.1016/j.eclinm.2026.104211

Image Credits: AI Generated

DOI: 10.1016/j.eclinm.2026.104211

Keywords: tumour-agnostic immunotherapy, MSI-H/dMMR, tumour mutational burden, checkpoint inhibitors, pembrolizumab, biomarkers, rare cancers, basket trials, Australia PBS reimbursement, precision oncology, tumour microenvironment, antibody-drug conjugates

The review, led by Ornella Gonzato with contributions from patient advocates Denise Reinke and Roger Wilson, oncologist Bernd Kasper and regulatory expert Maria Josefina Ruiz Alvarez, examines how two landmark frameworks can be operationalised in rare cancer research: the 2024 World Health Organization Guidance for best practices for clinical trials and the International Council for Harmonisation’s ICH E6(R3) Good Clinical Practice guideline. The WHO guidance articulates scientific validity, efficiency, ethical acceptability, social value, feasibility, equity and patient engagement as interdependent components of trial quality. ICH E6(R3) complements this by reframing Good Clinical Practice around quality by design and risk-proportionate oversight, emphasising critical-to-quality factors rather than box-ticking procedural compliance. Together, the authors argue, these documents shift trial governance toward principled flexibility.

The central problem is one of proportionality. When patient populations are intrinsically small and biologically fragmented, conventional fixed-sample randomised trials may impose disproportionate burdens on participants while offering only a slim probability of generating actionable knowledge. The WHO guidance explicitly ties ethical acceptability to proportionality between risk, burden and anticipated social value. Adaptive and Bayesian designs can improve efficiency while preserving methodological rigour, and the sarcoma field has become a proving ground for them. The biomarker-driven MULTISARC umbrella trial used centralised molecular profiling to allocate patients across treatment cohorts, showing how molecular stratification can enhance feasibility and interpretability even in highly fragmented populations. IMMUNOSARC employed a multicohort, single-arm design spanning multiple rare subtypes, illustrating how flexible, risk-proportionate approaches can support evidence generation when conventional randomisation is simply impractical.

But methodological innovation alone is not enough. The review emphasises that rare cancer research depends on collaborative infrastructure that often matters as much as the trial design itself. Cross-border networks such as the European Reference Network EURACAN and international sarcoma consortia enable accrual, harmonise standards and safeguard data quality. Multinational trials such as RAIN-3201, an international randomised phase III study, and rEECur, an international multi-arm seamless phase II/III trial in relapsed and refractory Ewing sarcoma, relied on coordinated governance, harmonised data collection and cross-border recruitment to maintain scientific validity while maximising the number of patients enrolled. In populations fragmented across dozens of subtypes, such infrastructures are frequently a prerequisite for adequately powered studies rather than a mere facilitator of research activity.

Equity emerges as a persistent tension throughout the analysis. Centralising expertise improves diagnostic accuracy and outcomes, but it can raise barriers to research participation. Travel burdens, financial costs and logistical complexity fall disproportionately on patients in rural regions, lower socioeconomic groups and older populations. Regulatory heterogeneity compounds the problem: in multinational rare cancer studies, variation in approval timelines, submission requirements and local governance procedures delays site activation and creates unequal opportunities for participation across countries. These asymmetries fall hardest on academic and investigator-initiated studies, which typically lack dedicated regulatory affairs departments. The authors point to ECRIN’s Regulatory and Ethical Database, which catalogues country-specific requirements across more than 750 searchable fields, as a practical tool for navigating this fragmentation, but they stress that differences in ethics committee composition, review timelines and national procedures persist alongside the EU’s Clinical Trials Information System harmonisation.

Decentralised and hybrid trial models offer a partial remedy. Remote informed consent, telemedicine visits, electronic patient-reported outcomes, local clinical assessments, remote monitoring and digital data capture can reduce the burden of participation for geographically dispersed patients, improving recruitment and retention. Registry-based initiatives such as RESAR, a prospective multicentre sarcoma registry, and ICONIC, a registry-based osteosarcoma platform with strong patient involvement, demonstrate how longitudinal real-world data collection can complement interventional studies, support external control arms when randomisation is infeasible and give researchers contextual evidence grounded in patient experience. The authors caution, however, that decentralisation should extend rather than replace specialist centres, and that digital-first approaches require infrastructure, regulatory alignment, data protection safeguards and explicit attention to digital inclusion so that efforts to improve accessibility do not unintentionally exclude under-resourced populations.

Patient-centredness, the review argues, is not merely an ethical nicety but a structural determinant of what the authors call operational validity—the ability of a trial to generate interpretable evidence under the real-world constraints of population size, feasibility and participation. In sarcomas, endpoints such as functional preservation and long-term toxicity may matter more to patients than short-term tumour response. The randomised multicentre surgical trial SarcoSIGHT shows that integrating functional and quality-of-life endpoints early in trial design is feasible while maintaining scientific rigour. Structured involvement of advocacy organisations such as the Sarcoma Patient Advocacy Global Network in protocol development, consent processes and dissemination enhances both feasibility and interpretability in very small populations, and patient-led initiatives like ICONIC demonstrate how engaged communities can shape research agendas and sustain engagement over time.

Digital and artificial intelligence-enabled tools extend this agenda further. Applications under active exploration include AI-assisted patient identification from electronic health records, wearable-based remote monitoring and digital twins as synthetic control alternatives—particularly relevant where randomising patients to a control arm is statistically or ethically constrained in ultra-rare populations. The WHO’s Global Action Plan for Clinical Trial Services calls for adopting such innovative designs and technologies to improve recruitment, data collection, analysis and oversight, while the Global Clinical Trials Forum provides the institutional architecture for aligning digital governance standards across jurisdictions. Yet the authors insist the governance risks demand equal attention: algorithmic bias can reproduce geographic and socioeconomic inequities in participant selection, unequal digital access can exclude vulnerable groups, and opaque AI-assisted decisions in eligibility or safety monitoring require audit trails and human oversight embedded by design.

The cross-cutting lessons are strikingly consistent. Methodological flexibility succeeds when linked to clear biological rationale, not innovation for its own sake. Feasibility and scientific validity are inseparable, because recruitment failure and attrition can render even a methodologically sound trial inconclusive. International collaborative infrastructure is an enabling condition, not a luxury. Patient-centred approaches improve operational performance, not just ethical acceptability. And despite all this progress, regulatory fragmentation remains the stubborn barrier that governance frameworks must address with greater specificity. The WHO Global Action Plan’s sixth action on streamlining regulatory and ethics review will need teeth if equitable, multinational rare cancer trials are to become routine rather than exceptional.

The implications reach well beyond sarcomas. As molecular stratification carves common cancers into progressively smaller and more dispersed subsets, the governance lessons forged in rare cancer research are increasingly relevant to precision oncology at large. The authors identify outstanding questions that will define the next decade: how to translate principles into proportionate governance across diverse regulatory systems, how to combine adaptive designs, registries, real-world data and decentralised models optimally, how to integrate patient involvement into regulatory decision-making, how to deploy digital tools equitably and transparently, and what sustainable funding models can maintain international research infrastructures. The review is candid about its limitations—it is a structured narrative synthesis, examples are illustrative rather than exhaustive, most evidence comes from high-income settings, and direct causal evidence linking patient engagement practices to trial outcomes remains limited. But its core message is clear: in rare cancers, operational validity depends on the interaction of methodological innovation, collaborative infrastructure, patient-centred governance and proportional regulation, and sarcoma research has shown the way.

Subject of Research: Patient-centred clinical trial design and governance for rare cancers, using sarcomas as a model for applying 2024 WHO guidance and ICH E6(R3)

Article Title: Patient-centred and fit-for-purpose clinical trials in rare cancers: lessons from sarcomas for operationalising 2024 WHO Guidance and ICH E6(R3)

Article References: Gonzato, O., Reinke, D., Wilson, R., Kasper, B., & Ruiz Alvarez, M. J. (2026). Patient-centred and fit-for-purpose clinical trials in rare cancers: lessons from sarcomas for operationalising 2024 WHO Guidance and ICH E6(R3). eClinicalMedicine, 100, Article 104192. https://doi.org/10.1016/j.eclinm.2026.104192

Image Credits: AI Generated

DOI: 10.1016/j.eclinm.2026.104192

Keywords: rare cancers, sarcoma, clinical trials, WHO guidance, ICH E6(R3), adaptive trial design, patient engagement, decentralised trials, real-world data, regulatory harmonisation, operational validity, precision oncology