The study, led by Xiang Pan and Ziting Su of the First Affiliated Hospital of Dali University in Yunnan, China, and published in BMC Cancer, systematically evaluated clinical practice guidelines on precision oncology in biliary tract cancers using two internationally recognised appraisal instruments, AGREE II and AGREE-REX. The team searched eight databases and thirteen guideline repositories and society websites, capturing guidance published or updated between January 2016 and June 2026. From thirty individual reports, the researchers assembled twenty-seven distinct guideline families, which they then subjected to independent appraisal by three trained assessors.

What makes this analysis technically distinctive is the decision to separate two halves of the precision oncology pathway that guidelines frequently blur together: molecular testing and biomarker-directed treatment. The authors argue that precision medicine in biliary tract cancer requires more than merely listing actionable biomarkers. A complete guideline must connect the who and how of testing to the treatment or clinical trial action that follows a positive result. By applying separate AGREE-REX appraisal clusters for testing and treatment recommendations, and by mapping cross-guideline support across a prespecified twelve-topic matrix, the team created one of the most granular portraits to date of how well guidance documents serve the full genomic care pathway.

The AGREE II results reveal a striking asymmetry in guideline quality. The strongest domain was clarity of presentation, with a median score of 98.1 percent, followed by scope and purpose at 88.9 percent. In other words, when a guideline makes a recommendation, it usually states it clearly. But the infrastructure around those recommendations was consistently weaker. Patient and public involvement, methods for updating, monitoring and audit provisions, and external review all scored poorly across the field. These are the domains that determine whether a guideline remains trustworthy as evidence evolves, whether it reflects what patients actually value, and whether institutions can verify that recommendations are being followed in practice.

The AGREE-REX appraisal, which drills down to the quality of individual recommendations rather than whole documents, surfaced another weakness: values and preferences was the lowest-scoring domain in both the testing and treatment clusters. This finding suggests that guideline developers are not systematically describing the evidence underlying patient values and treatment preferences when they craft recommendations. For patients facing choices between cytotoxic chemotherapy, targeted agents, or clinical trial enrolment, that gap is more than an academic shortcoming.

On the substantive question of which biomarkers enjoy the broadest guideline support, the picture is clear. Broad molecular profiling using next-generation sequencing was supported by eighteen of twenty-seven guideline families, reflecting a growing consensus that comprehensive genomic testing, rather than single-gene assays, is the appropriate strategy in this disease. On the treatment side, the highest support went to microsatellite instability-high or mismatch repair-deficient tumours, endorsed by twenty of twenty-seven families, followed by FGFR2 alterations at seventeen and IDH1 mutations at sixteen. HER2-directed therapy was supported by twelve of twenty-six families after one unclassifiable unit was excluded. These targets map directly onto approved therapies and the antibody-drug conjugates now reshaping the treatment landscape for HER2-positive disease.

Perhaps the most consequential finding is that testing and treatment support frequently diverged. Several biomarker-treatment pairings were endorsed as therapies without corresponding guidance on molecular testing, and vice versa. A clinician reading one of these guidelines might learn that an IDH1 inhibitor is appropriate for a patient with an IDH1-mutant tumour, yet find no recommendation on how or when to test for that mutation. The authors are careful to note that such divergent coverage does not itself indicate lower recommendation quality; rather, it reveals structural incompleteness. Guidelines excel at the endpoint of the pathway while leaving the intermediate steps, the testing indications, timing, and methods, underspecified.

The review also demonstrates methodological rigour in its own appraisal process. Historical intraclass correlation coefficients across the appraisal rounds ranged from 0.918 to 0.960, indicating near-perfect agreement among the three independent assessors. A separate revision-stage sensitivity analysis incorporating de novo ratings for a subset of twenty-two families yielded a coefficient of 0.925. Sensitivity analyses that counted clinical-trial-only recommendations alongside explicit and conditional recommendations further tested the robustness of the coverage findings. The study was prospectively registered with PROSPERO under registration number CRD420261438683, and the search strategy was peer-reviewed according to the PRESS standard.

The implications for clinical practice are immediate. Biliary tract cancers are diagnosed in roughly hundreds of thousands of people worldwide each year, and outcomes remain poor, with many patients presenting at advanced stages where molecularly informed decisions carry the greatest weight. For oncologists navigating this landscape, the review functions as a meta-map: it identifies which guidelines provide the most complete testing-to-treatment pathways and where the consensus on targets such as MSI-H/dMMR, FGFR2, and IDH1 is strongest. It also flags where clinicians must supplement guideline advice, for instance by consulting molecular tumour boards or trial registries when testing guidance is absent.

For guideline developers, the authors offer a clear blueprint for the next generation of documents. Future guidance, they conclude, should explicitly link testing indication, timing, and method to post-test clinical action, while strengthening patient involvement, evidence-to-decision reporting, resource-sensitive implementation strategies, audit indicators, conflict of interest management, and prospective updating mechanisms. The finding that no external funding supported the research, with study expenses personally covered by the corresponding author, adds a note of independence to a field where commercial interests in genomic testing and targeted therapies are considerable. As precision oncology matures, the bottleneck may no longer be discovering new biomarkers but ensuring that the documents meant to translate them into bedside decisions are as rigorous, complete, and current as the science they describe.

Subject of Research: Quality appraisal of clinical practice guidelines for precision oncology in biliary tract cancers

Article Title: Quality of clinical practice guidelines on precision oncology in biliary tract cancers: a systematic review using AGREE II and AGREE-REX

Article References: Pan, X., An, Q., Liu, J., Zhang, S., Long, Y., Jiang, J., & Su, Z. (2026). Quality of clinical practice guidelines on precision oncology in biliary tract cancers: a systematic review using AGREE II and AGREE-REX. BMC Cancer. https://doi.org/10.1186/s12885-026-17168-8

Image Credits: AI Generated

DOI: 10.1186/s12885-026-17168-8

Keywords: biliary tract cancer, precision oncology, clinical practice guidelines, AGREE II, AGREE-REX, cholangiocarcinoma, next-generation sequencing, FGFR2, IDH1, MSI-H/dMMR, HER2, systematic review

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