The research team, led by investigators at Beijing University of Chinese Medicine and Peking University Third Hospital, systematically searched PubMed, Embase, and the Cochrane Library through 6 November 2025. From an initial haul of 1,180 records, they identified ten randomized controlled trials encompassing 3,959 patients with metastatic colorectal cancer who had progressed after second-line therapy. Each trial compared one of the three oral agents—alone or, in some cases, TAS-102 combined with bevacizumab—against placebo or best supportive care. Risk of bias was assessed with the Cochrane RoB-2 tool, and the protocol was prospectively registered with PROSPERO.

Because no trial has ever randomized patients directly between regorafenib, fruquintinib, and TAS-102, the researchers turned to network meta-analysis, a statistical framework that uses a common comparator—in this case placebo—to make indirect comparisons across trials. They fitted a Bayesian random-effects consistency model with non-informative normal priors, ran four parallel Markov chains through 20,000 adaptation iterations and 50,000 sampling iterations, and confirmed convergence using the Gelman-Rubin diagnostic. The resulting network was star-shaped, anchored on placebo, with no closed loops among the active treatments, which meant formal inconsistency testing was impossible; instead, the team relied on transitivity checks comparing trial characteristics and potential effect modifiers.

The headline finding for the overall population was straightforward: every active treatment significantly prolonged overall survival compared with placebo. Fruquintinib produced a hazard ratio of 0.66 (95% credible interval 0.53–0.84), regorafenib 0.69 (0.51–0.88), TAS-102 0.69 (0.55–0.85), and TAS-102 plus bevacizumab 0.41 (0.28–0.59). The combination of TAS-102 with bevacizumab ranked first by SUCRA—the surface under the cumulative ranking curve—while the three single agents showed broadly similar efficacy, with indirect differences among them not consistently statistically significant. Progression-free survival followed the same pattern, with all experimental arms outperforming placebo and the doublet again delivering the largest benefit.

One indirect comparison did stand out: fruquintinib showed a more favorable progression-free survival than TAS-102, with a hazard ratio of 0.65 (95% CrI 0.45–0.96), placing it highest among the monotherapies. The authors caution, however, that this estimate rests entirely on indirect evidence in the absence of head-to-head trials and should be interpreted cautiously. Heterogeneity also varied considerably across the network: it was essentially absent for fruquintinib versus placebo (I² ≈ 0%), moderate for TAS-102 (OS I² = 21.8%), and high for regorafenib (OS I² = 67.5%, PFS I² = 83.1%), prompting the use of random-effects models throughout.

The most novel contribution of the analysis lies in its KRAS stratification. During transitivity checks, KRAS mutational status emerged as the most plausible source of the between-study heterogeneity, driven largely by differences in baseline KRAS prevalence—Asian trials such as CONCUR and TERRA enrolled 34% and 37% KRAS-mutant patients respectively, while the remaining trials ranged from 40% to 70%. When the team restricted the analysis to trials reporting KRAS-subgroup overall survival data, heterogeneity collapsed dramatically in the wild-type subgroup, with I² falling to 20% or below for every comparison, and the three agents ranked almost side by side with no meaningful differences between them.

In the KRAS-mutant subgroup, the picture shifted subtly. Fruquintinib and TAS-102 each produced numerically favorable overall survival estimates versus placebo—hazard ratios of 0.71 (95% CrI 0.51–1.01) and 0.74 (95% CrI 0.50–0.99) respectively—whereas regorafenib did not reach statistical significance, with a hazard ratio of 0.81 (95% CrI 0.52–1.19). The exploratory ranking placed fruquintinib first, TAS-102 second, and regorafenib last. The authors are emphatic, however, that these differences in statistical significance versus placebo do not demonstrate superiority of fruquintinib or TAS-102 over regorafenib, and that the rank probabilities are hypothesis-generating rather than evidence of a predictive effect of KRAS status.

The mechanistic backdrop helps explain why KRAS status might matter. KRAS is mutated in approximately 40% of colorectal cancers, driving constitutive RAS signaling and unrestrained cell growth. Prior laboratory work has suggested that exon-2 KRAS mutations, particularly G12C and G12A, maintain elevated BRAF-ERK-ELK phosphorylation and blunt regorafenib-induced apoptosis and vessel shutdown, while a recently described KRAS/ERK2–TRIM21–c-Myc/ENO2 glycolytic axis promotes regorafenib resistance. Notably, among the three TAS-102 trials, the Japanese phase 2 study by Yoshino and colleagues showed a markedly stronger benefit in KRAS-mutant patients (hazard ratio 0.44) than in wild-type disease (0.70), a pattern that largely accounts for the residual heterogeneity in that treatment node.

The combination of TAS-102 with bevacizumab emerged as the standout regimen overall. Mechanistically, the pairing is plausible: trifluridine inhibits thymidylate synthase and, through its metabolite FTY, becomes incorporated into DNA causing miscoding, while tipiracil protects trifluridine from degradation by blocking thymidine phosphorylase; bevacizumab, meanwhile, suppresses VEGF-driven angiogenesis and remodels the tumor microenvironment. The authors suggest these mechanisms may act synergistically, and a separate analysis indicated the combination conferred a particularly pronounced survival benefit in RAS-mutant patients (hazard ratio 0.38, 95% CrI 0.19–0.79) with no significant advantage over monotherapy in the wild-type population—though only one study contributed to that subgroup node, precluding a stable network estimate.

The study has clear limitations that the authors acknowledge candidly. No head-to-head randomized comparisons exist among the three agents, the star-shaped network precluded formal inconsistency testing, and individual-participant data were unavailable, so a formal treatment-by-KRAS interaction test could not be performed. Comparative safety was not formally meta-analyzed because safety definitions and reporting thresholds differed substantially across trials, and progression-free survival subgroup analysis was abandoned due to insufficient sample size and high heterogeneity (I² ranging from 77.7% to 92.2%). Publication-bias testing was deemed unreliable with fewer than ten trials per outcome. The authors conclude that for KRAS-wild-type patients, standard third-line regimens or TAS-102 plus bevacizumab are reasonable, while for KRAS-mutant patients fruquintinib may represent a sensible later-line option—pending confirmation from prospective, KRAS-stratified or head-to-head trials that the field has yet to deliver.

Subject of Research: Comparative efficacy of third-line oral therapies for KRAS-mutant metastatic colorectal cancer

Article Title: Comparative efficacy of fruquintinib, regorafenib or TAS-102 in patients with KRAS-mutant metastatic colorectal cancer: a systematic review and network meta-analysis

Article References: Zhou, Y., Zhao, S., Zheng, X., Wang, Y., Wang, M., Chen, S., Wu, Z., Zang, D., & Si, W. (2026). Comparative efficacy of fruquintinib, regorafenib or TAS-102 in patients with KRAS-mutant metastatic colorectal cancer: a systematic review and network meta-analysis. Frontiers in Oncology, 16, Article 1948508. https://doi.org/10.3389/fonc.2026.1948508

Image Credits: AI Generated

DOI: 10.3389/fonc.2026.1948508

Keywords: fruquintinib, regorafenib, TAS-102, KRAS mutation, metastatic colorectal cancer, network meta-analysis, overall survival, progression-free survival, bevacizumab, third-line therapy, precision oncology, Bayesian analysis

Hepatocellular carcinoma, the most common form of liver cancer, is notorious for its silent progression. Global cancer statistics from 2018 ranked liver cancer as the sixth most common malignancy and the fourth leading cause of cancer death worldwide. Because most patients are diagnosed only after the disease has reached intermediate or advanced stages, surgical resection is often no longer an option. For these individuals, treatment relies on non-curative approaches such as chemotherapy, targeted drug therapy, and immunotherapy, making any improvement in the effectiveness of these tools a matter of life and death.

Tyrosine kinase inhibitors, or TKIs, form the backbone of pharmacological treatment for advanced liver cancer. First-line drugs such as sorafenib and lenvatinib block the signaling pathways that tumor cells use to proliferate and survive, but many patients eventually progress or develop resistance. Regorafenib, approved by the U.S. Food and Drug Administration in 2017 for patients whose disease advances on sorafenib, targets a broad panel of receptors including VEGFR1-3, PDGFR-beta, KIT, RET, and RAF, and uniquely also hits fibroblast growth factor receptors and the angiopoietin 1 receptor known as TIE2. Preclinical work has suggested regorafenib is pharmacologically more potent than sorafenib, capable of blocking angiogenesis, tumorigenesis, and metastasis while also modulating tumor immunity. Earlier studies showed it can drive liver cancer cells into apoptosis by directly activating the phosphatase SHP-1, which suppresses phosphorylated STAT3, an effect independent of its anti-angiogenic activity.

On the immunotherapy side, the team turned to BMS-1, a small molecule first described in a 2015 patent filed by Bristol-Myers Squibb as part of a series of compounds that disrupt the interaction between the immune checkpoint proteins PD-1 and PD-L1. Antibody drugs such as atezolizumab and avelumab have shown promise against several malignancies, but antibodies suffer from drawbacks including immunogenicity and poor penetration of tumor tissue, which contribute to low response rates in some patients. Small-molecule checkpoint inhibitors could, in principle, sidestep these limitations, and combining them with other agents has become an active research frontier.

To test whether BMS-1 truly engages its intended target, the researchers first ran molecular docking simulations using AutoDock Vina software. The predicted binding energy of the BMS-1-PD-L1 complex was a favorable minus 11.633 kilocalories per mole, and the structural model placed BMS-1 wedged between PD-L1 dimers, consistent with the idea that the compound prevents the ligand from engaging PD-1 on T cells. The team then measured how effectively each drug killed three human hepatocellular carcinoma cell lines, SMMC-7721, Hep3B, and SK-Hep1, using CCK-8 viability assays. The half-maximal inhibitory concentrations came out at roughly 13.35, 13.32, and 9.50 micromolar for regorafenib, and 74.11, 73.08, and 53.76 micromolar for BMS-1 across the three lines, establishing dose ranges for combination testing.

When the drugs were combined at concentrations below each one’s IC50, the results were striking. Using CompuSyn software to calculate combination indices, the team found values below 1, the mathematical signature of synergy rather than simple additivity, in SMMC-7721 cells across the tested combinations, and in Hep3B and SK-Hep1 cells for most combinations. The pairing of 6 micromolar regorafenib with 30 micromolar BMS-1 showed synergy in all three cell lines and was selected for deeper analysis. Transwell assays added another dimension: regorafenib alone significantly curbed the migration and invasion of the cancer cells, BMS-1 alone had little effect, and the combination suppressed these malignant behaviors even more strongly than regorafenib by itself.

Digging into the mechanism, the researchers tracked how the drug pair altered cell cycle machinery. EdU incorporation assays revealed a sharp drop in the fraction of cells in S phase after combination treatment, and western blotting showed that levels of Cyclin A2, Cyclin B1, Cyclin D1, and Cyclin D3, the proteins that drive cells through the G1/S and G2/M checkpoints, were downregulated, with Cyclin A2 and Cyclin B1 significantly lower in the combination group than with either drug alone. Apoptosis assays told a parallel story. Flow cytometry with Annexin V and propidium iodide staining, backed up by TUNEL staining, showed that the combination produced the highest rate of late apoptosis in all three cell lines, while western blots revealed a marked increase in cleaved PARP, a canonical executioner of programmed cell death, and a decrease in the proliferation marker PCNA.

One of the most intriguing findings emerged when the team introduced immune cells into the picture. Hepatocellular carcinoma cells barely expressed PD-L1 when grown alone, but when the researchers co-cultured them with peripheral blood mononuclear cells isolated from healthy volunteers, PD-L1 expression surged, mimicking the immune pressure of a real tumor microenvironment. Under those conditions, regorafenib pushed PD-L1 levels down, BMS-1 had a modest effect, and the combination drove PD-L1 expression down significantly. The authors speculate that regorafenib’s shared target FGFR4, which lenvatinib uses to promote proteasomal degradation of PD-L1 through the FGFR4-glycogen synthase kinase 3-beta pathway, may underlie this effect, though they caution that the exact mechanism remains unproven.

The combination also held up in living animals. In nude mice bearing subcutaneous tumors derived from SMMC-7721 cells, four weeks of treatment with intraperitoneal BMS-1 at 20 milligrams per kilogram twice weekly plus oral regorafenib at 5 milligrams per kilogram five times weekly shrank tumor volume and weight more dramatically than either drug alone. The authors are careful to note the caveats: the xenograft model lacks a fully functional immune system, so the immunological component of the synergy could not be fully assessed, and systemic tolerability has yet to be evaluated prospectively. They also point to related work suggesting that BMS-series compounds and other biphenyl derivatives can trigger cancer cell death through non-immune pathways, such as inhibition of AKT phosphorylation or modulation of TGF-beta/Smad signaling, hinting that BMS-1 may be doing double duty.

Even so, the study adds momentum to one of the hottest ideas in oncology: that molecularly targeted drugs can remodel the tumor microenvironment in ways that make immune checkpoint blockade work better. Prior research has shown that regorafenib can boost CD8-positive T cell activation by blocking interferon-gamma-induced PD-L1 expression in melanoma, and that combining kinase inhibitors with checkpoint inhibitors can allow cytotoxic T lymphocytes to infiltrate tumors more effectively. With single-agent checkpoint inhibitors such as nivolumab and pembrolizumab delivering median overall survival of only 15.6 and 12.9 months in liver cancer trials, respectively, the need for better combinations is acute. If future studies in immunocompetent models and eventually patients confirm what the cell cultures and mouse xenografts suggest, the regorafenib-BMS-1 pairing could provide a theoretical foundation for a new generation of chemo-immunotherapy against hepatocellular carcinoma, one in which a kinase inhibitor and a checkpoint blocker amplify each other’s strengths while keeping doses, and side effects, in check.

Subject of Research: Combination therapy with regorafenib and the small-molecule PD-1/PD-L1 inhibitor BMS-1 for hepatocellular carcinoma

Article Title: BMS-1 synergistically promotes the anti-tumor effect of regorafenib on hepatocellular carcinoma

Article References: Yu, G., Li, J., Wang, K., Fu, F., Lin, J., Xu, W., Liu, S., & Yang, H. (2026). BMS-1 synergistically promotes the anti-tumor effect of regorafenib on hepatocellular carcinoma. Heliyon, 12(15), Article e45420. https://doi.org/10.1016/j.heliyon.2026.e45420

Image Credits: AI Generated

DOI: 10.1016/j.heliyon.2026.e45420

Keywords: hepatocellular carcinoma, regorafenib, BMS-1, PD-1/PD-L1 inhibitors, tyrosine kinase inhibitors, immunotherapy, combination therapy, apoptosis, cell cycle, tumor microenvironment, xenograft model, synergy

Metastatic colorectal cancer remains one of the most common causes of cancer death worldwide. According to estimates cited by the study’s authors from the International Agency for Research on Cancer, colorectal cancer accounts for a substantial share of new cancer diagnoses globally, and Japan, where the study was conducted, maintains detailed national cancer statistics reflecting the disease’s heavy burden. Once patients progress through initial chemotherapy regimens and targeted combinations, they enter a refractory stage where only a handful of options remain. Regorafenib, an oral multikinase inhibitor that blocks tumor angiogenesis and oncogenic signaling pathways, and trifluridine/tipiracil, an oral nucleoside antimetabolite combination that thwarts tumor DNA repair, are the two pillars of this late-line setting. Both extend survival compared with placebo in randomized trials, but no definitive evidence had established which sequence delivers better outcomes when both drugs are ultimately available to a patient.

The OSERO study, led by Takeshi Kawakami of the Shizuoka Cancer Center with Eiji Oki of Kyushu University serving as principal investigator, was designed to close that evidence gap prospectively rather than retrospectively. Sponsored by the Kyushu Study group of Clinical Cancer and funded by Bayer Yakuhin, the study enrolled patients across 42 Japanese institutions who were scheduled to begin later-line treatment with regorafenib or trifluridine/tipiracil, with or without bevacizumab. Patients were assigned to three cohorts: cohort A received regorafenib monotherapy, cohort B received trifluridine/tipiracil alone, and cohort C received trifluridine/tipiracil plus bevacizumab, an anti-VEGF antibody that starves tumors of their blood supply. The primary endpoint was overall survival, the most clinically meaningful measure of whether a treatment sequence prolongs life.

In total, 468 patients were analyzed, with 154 in the regorafenib cohort, 82 in the trifluridine/tipiracil cohort, and 232 in the trifluridine/tipiracil plus bevacizumab cohort. The raw numbers told an initially striking story. Patients starting with regorafenib had a median overall survival of 12.2 months, compared with 7.5 months for those starting with trifluridine/tipiracil alone and 10.6 months for those receiving the combination with bevacizumab. Rates of proceeding to a scheduled second-line treatment also differed markedly: 65.6 percent of regorafenib starters went on to further therapy, compared with 37.8 percent of the trifluridine/tipiracil-alone group and 62.9 percent of the bevacizumab combination group.

But raw comparisons in observational research are notoriously misleading. Clinicians do not assign these drugs at random; they weigh each patient’s performance status, prior treatment history, organ function, and the aggressiveness of the disease. Patients selected for one drug may be systematically healthier or sicker than those selected for another, a phenomenon known as confounding by indication. To address this, the investigators applied stabilized inverse probability of treatment weighting, a statistical technique derived from propensity score modeling. Each patient was assigned a weight reflecting the probability of receiving the treatment they actually received given their baseline characteristics, effectively creating a pseudo-population in which treatment assignment was independent of measured confounders. This method, widely used in pharmacoepidemiology, cannot eliminate bias from unmeasured variables, but it represents the strongest adjustment feasible outside a randomized trial.

After this adjustment, the survival difference between the two principal strategies evaporated. Median overall survival was 12.2 months for the regorafenib-first sequence and 10.6 months for the trifluridine/tipiracil-plus-bevacizumab sequence, with a hazard ratio of 1.03 and a 95 percent confidence interval of 0.81 to 1.30, and a P value of 0.837. A hazard ratio so close to 1.0, with a confidence interval comfortably spanning unity, indicates essentially no detectable survival advantage for either sequence. In practical terms, the total length of survival a patient could expect from the two-drug sequence appeared similar regardless of which agent was deployed first.

The safety data, however, revealed a sharp and clinically consequential divide. Grade 3 or higher adverse events occurring in more than 10 percent of patients differed by cohort. In the regorafenib group, the dominant toxicities were hand-foot syndrome, proteinuria, and hypertension, classic signatures of the drug’s anti-angiogenic and multikinase activity. Hand-foot syndrome, a painful inflammation of the palms and soles, can severely limit daily function and often forces dose reductions. In the trifluridine/tipiracil groups, both with and without bevacizumab, the principal toxicities were hematologic: neutropenia, a depletion of infection-fighting white blood cells, and anemia. These contrasting profiles mean that the two strategies impose different burdens on different patients, and the authors concluded that treatment selection may reasonably depend on the safety profile of each drug in the context of individual patient characteristics.

The findings arrive at a moment when the late-line colorectal cancer landscape is shifting. The addition of bevacizumab to trifluridine/tipiracil gained momentum after a series of Japanese investigator-initiated studies, including the C-TASK FORCE, TAS-CC3, TAS-CC4, and BiTS trials, demonstrated the feasibility and activity of the combination. That momentum culminated in the international phase 3 SUNLIGHT trial published in the New England Journal of Medicine in 2023, which showed that trifluridine/tipiracil plus bevacizumab improved survival over trifluridine/tipiracil alone in refractory disease, cementing the combination in international guidelines from the National Comprehensive Cancer Network and the European Society for Medical Oncology. Meanwhile, the FRESCO-2 trial introduced fruquintinib, another oral angiogenesis inhibitor, as a further option, and earlier work such as the Japanese REGOTAS propensity score analysis had attempted retrospective comparisons of regorafenib and trifluridine/tipiracil. Prior work by several of the same OSERO investigators had also suggested that survival benefits accumulate with the number of active drugs a patient receives, underscoring why sequencing questions matter so much.

What distinguishes OSERO is its prospective design. Most evidence comparing these agents has come from retrospective chart reviews or registry analyses, which are vulnerable to selection bias and incomplete data. By registering patients before treatment began, at the moment the clinician committed to a strategy, the investigators captured the true decision point of interest. The study was conducted in accordance with the Declaration of Helsinki, approved by the Kyushu University institutional review board, and all participants provided written informed consent. The breadth of participation, spanning 42 institutions from Shizuoka to Hokkaido to Kyushu, lends the results a real-world texture that single-center trials often lack, reflecting the heterogeneous patient populations and clinical judgments that define everyday oncology practice.

For clinicians, the message is one of flexibility rather than a new mandate. Because the two sequences yielded comparable adjusted survival, oncologists can tailor the choice to the patient in front of them: a patient with poorly controlled hypertension or painful hand-foot syndrome risk factors might be steered toward trifluridine/tipiracil with bevacizumab, while one with marginal bone marrow reserve might better tolerate regorafenib. For patients, the study offers reassurance that neither choice forecloses a meaningful survival opportunity, since both drugs can typically be delivered in sequence. The authors caution that, as an observational study, OSERO cannot rule out residual confounding, and randomized confirmation remains the gold standard. Yet with a randomized head-to-head sequencing trial unlikely to be mounted, this prospectively collected, statistically adjusted evidence from nearly 500 patients stands as the clearest guidance available, and it suggests that in the final chapters of metastatic colorectal cancer treatment, the order of the last two drugs matters far less than ensuring patients can safely receive both.

Subject of Research: Treatment sequencing of regorafenib and trifluridine/tipiracil in later-line metastatic colorectal cancer

Article Title: A prospective observational study of treatment sequencing with regorafenib and FTD/TPI in metastatic colorectal cancer: The OSERO study

Article References: A prospective observational study of treatment sequencing with regorafenib and FTD/TPI in metastatic colorectal cancer: The OSERO study. (n.d.). https://doi.org/10.1038/s41416-026-03620-w

Image Credits: AI Generated

DOI: 10.1038/s41416-026-03620-w

Keywords: metastatic colorectal cancer, regorafenib, trifluridine/tipiracil, bevacizumab, treatment sequencing, overall survival, observational study, propensity score, inverse probability weighting, chemotherapy, drug safety, clinical oncology

Hand-foot syndrome, or PPE, is far more than a cosmetic nuisance. The condition typically begins with tingling, numbness and redness on the palms of the hands and soles of the feet, and can progress in severe cases to swelling, blistering, ulceration and intense pain that makes walking, gripping objects or even buttoning a shirt difficult. Because these symptoms strike exactly the functions patients rely on for daily life, PPE is a leading cause of dose reductions, treatment interruptions and outright abandonment of otherwise effective cancer regimens. Oncologists have long recognized it as a hallmark toxicity of certain targeted therapies and chemotherapy agents, but the true breadth of drugs implicated — and the timing of onset — has remained surprisingly poorly mapped.

To build that map, the researchers turned to FAERS, the FDA’s sprawling spontaneous reporting database, which collects adverse event submissions from healthcare professionals, manufacturers and patients across the United States. They extracted reports spanning the first quarter of 2004 through the first quarter of 2025, removed duplicate submissions, and then applied a family of statistical techniques known as disproportionality analysis. Rather than proving causation in the way a clinical trial would, disproportionality analysis asks a subtler question: does a particular drug appear in reports of a given side effect more often than would be expected by chance? Four complementary algorithms were used to answer that question — the reporting odds ratio, the proportional reporting ratio, the Bayesian confidence propagation neural network and multi-gamma Poisson shrinkage. Requiring agreement across all four methods helps filter out spurious associations that can arise in self-reported data.

The results were striking in both their scale and their specificity. Protein kinase inhibitors — the targeted drugs that block enzymes driving cancer cell growth and tumor blood vessel formation — and antimetabolites, the classic chemotherapy agents that interfere with DNA and RNA synthesis, emerged as the dominant drug classes. Among individual agents, the oral kinase inhibitor regorafenib, the multi-kinase blocker sorafenib and the fluoropyrimidine prodrug capecitabine produced the strongest safety signals. These three drugs are mainstays of treatment for colorectal cancer, hepatocellular carcinoma, renal cell carcinoma and other hard-to-treat malignancies, meaning the toxicity burden is concentrated in some of oncology’s most vulnerable populations. The finding that hundreds of other drugs also appeared in PPE reports underscores that the syndrome is not confined to a short list of notorious culprits.

Perhaps the most clinically actionable discovery concerns timing. The vast majority of PPE cases — 83.4 percent — occurred within the first 90 days of starting treatment, with many surfacing within the initial weeks. This early-onset pattern carries an important message for oncology teams: the highest-risk window for hand-foot syndrome opens almost immediately after a patient begins therapy. The authors argue that this argues for proactive patient education at the very first prescription, so that patients recognize the earliest tingling or redness and report it before it escalates into blistering lesions. It also supports intensified skin assessment during the initial phases of treatment with high-risk drugs, when a timely dose adjustment can often prevent progression without compromising cancer control.

The analysis also uncovered differences in reporting patterns between female and male patients. For two drugs in particular — the HER2-targeted breast cancer therapy lapatinib and capecitabine — PPE signals were stronger in women. The researchers are careful to caution against overinterpreting this finding. Sex-related differences in spontaneous reports can arise from prescribing patterns, with some drugs used predominantly in diseases that affect one sex more than the other, as well as from possible biological factors such as differences in skin structure, drug metabolism or hormonal influences. Disentangling genuine biological susceptibility from the artifacts of who receives which drug and who reports which symptom remains an open challenge for pharmacovigilance, and the authors explicitly call for cautious interpretation and further study.

Mechanistically, hand-foot syndrome is thought to arise from the unique biology of the skin on the palms and soles. These regions are rich in eccrine sweat glands, experience high mechanical pressure and friction, and express high levels of the molecular targets — such as vascular endothelial growth factor receptor and platelet-derived growth factor receptor — that protein kinase inhibitors are designed to block. When those signaling pathways are inhibited in the skin’s blood vessels, capillary damage and local inflammation can follow, and the repeated trauma of walking and gripping amplifies the injury. For antimetabolites like capecitabine, which is converted to 5-fluorouracil inside the body, the toxicity reflects the drug’s interference with rapidly dividing cells, with the concentration of the activating enzyme thymidine phosphorylase particularly high in palm and sole tissue. The convergence of drug exposure and mechanical stress explains why the syndrome has such a distinctive anatomical fingerprint.

The scale of the new study gives it particular weight in a field where much of the evidence comes from small clinical trials that may not capture rare or slowly accumulating toxicities. By pooling more than two decades of real-world reports, the analysis captures the experience of a far more diverse patient population than any single trial — patients with comorbidities, concurrent medications and varying ethnic backgrounds. At the same time, the authors and pharmacovigilance experts alike emphasize the inherent limitations of spontaneous reporting: not all adverse events are reported, reporting rates are influenced by media attention and litigation, and the database cannot establish how frequently PPE occurs relative to the total number of patients treated. Disproportionality signals are a starting point for hypothesis generation, not a verdict on causation.

Even with those caveats, the study’s implications for clinical practice are concrete. Oncologists prescribing regorafenib, sorafenib or capecitabine now have robust, data-driven backing for early and sustained skin monitoring, and the identification of 427 drugs with PPE reports should prompt awareness beyond the usual suspects, particularly as newer kinase inhibitors reach the market. For patients, the message is empowering: symptoms in the hands and feet during cancer treatment should never be dismissed as minor, because early recognition opens the door to dose modification, topical therapies, cooling measures and supportive care that can keep treatment on track. The research team concludes that enhanced vigilance and tailored monitoring schedules — matched to each drug’s risk profile and to the early onset window — are the most promising route to reducing the burden of this debilitating toxicity while preserving the anticancer benefits of the drugs patients depend on.

Subject of Research: Drug-induced palmar-plantar erythrodysaesthesia syndrome associated with antineoplastic agents identified through FDA adverse event reporting data

Article Title: Antineoplastic agent-induced palmar-plantar erythrodysaesthesia syndrome: insights from the FDA adverse event reporting system

Article References: Cheng, H., Li, Q., Hong, X., Zhang, Z., Chen, L., Yang, X., Wang, S., & Pan, W. (2026). Antineoplastic agent-induced palmar-plantar erythrodysaesthesia syndrome: insights from the FDA adverse event reporting system. Journal of Cancer Research and Clinical Oncology. https://doi.org/10.1007/s00432-026-06547-0

Image Credits: AI Generated

DOI: 10.1007/s00432-026-06547-0

Keywords: hand-foot syndrome, palmar-plantar erythrodysaesthesia, FAERS, pharmacovigilance, protein kinase inhibitors, capecitabine, regorafenib, sorafenib, antineoplastic agents, disproportionality analysis, adverse drug reactions, oncology