Real-world outcomes of chemotherapy in pancreatic cancer: considerations for validity and interpretation

I read with considerable interest the registry-based analysis by Engelke and colleagues (1), which evaluates outcomes associated with FOLFIRINOX (5-fluorouracil, leucovorin, oxaliplatin, and irinotecan) compared with gemcitabine and gemcitabine plus paclitaxel in patients with pancreatic cancer. Drawing on data from 3,919 individuals diagnosed between 2019 and 2021, the authors report lower mortality with FOLFIRINOX and improved survival with gemcitabine plus paclitaxel relative to gemcitabine alone in stage IV disease. These findings are broadly concordant with clinical trial data and add valuable real-world insight by capturing treatment patterns beyond conventional study populations.

Several methodological issues, however, warrant further discussion. Foremost is the likelihood of confounding by indication. Only about one-third of patients had performance status documented, despite its central role in regimen selection. Patients considered suitable for FOLFIRINOX are typically younger and fitter, and incomplete capture of Eastern Cooperative Oncology Group (ECOG) status risks exaggerating apparent survival differences. Sensitivity analyses such as the E-value, now widely recommended in comparative-effectiveness research, could have provided readers with a quantitative assessment of the robustness of the observed associations to unmeasured confounding (2).

Second, the proportional-hazards assumption underlying Cox models merits explicit testing. If treatment effects vary over time, a single hazard ratio may obscure clinically relevant dynamics. Use of Schoenfeld residuals, time-varying coefficients, or restricted mean survival time would enhance the accuracy and clinical interpretability of the survival comparisons (3).

Third, missing data and classification issues pose potential threats to validity. Stage was unavailable for most patients, and a large group had “no chemotherapy recorded”. These gaps introduce possible misclassification and biased estimates. Methods such as multiple imputation for missing stage, calendar-time-adjusted models, and sensitivity analyses reassigning a proportion of “untreated” patients could help quantify this uncertainty. Adherence to RECORD (REporting of studies Conducted using Observational Routinely-collected health Data) standards would also strengthen transparency by clarifying variable definitions, data completeness, and registry procedures (4).

Fourth, the study period coincided with the coronavirus disease 2019 (COVID-19) pandemic, which profoundly disrupted cancer care worldwide. Pandemic-related diagnostic delays, treatment interruptions, and excess mortality likely influenced outcomes. Adjusting for calendar time or stratifying analyses into pandemic phases could help disentangle regimen effects from contemporaneous external shocks (5).

Finally, placing these findings within the broader therapeutic landscape would further contextualize their relevance. Recent meta-analyses have shown superior survival with intensified regimens such as FOLFIRINOX or NALIRIFOX (5-fluorouracil, leucovorin, liposomal irinotecan, and oxaliplatin) compared with gemcitabine plus nab-paclitaxel in appropriately selected patients (6). International guidelines likewise prioritize FOLFIRINOX or related triplet regimens as first-line options in fit patients (7). Explicitly contrasting registry-based estimates with these external benchmarks would help readers appreciate both the consistency and limitations of the data.

At the same time, registry data offer a uniquely valuable complement to randomized evidence by reflecting treatment delivery and outcomes across the full spectrum of real-world practice. Beyond statistical modeling, longitudinal analyses can illuminate patient subgroups—defined by age, comorbidity, or socioeconomic factors—who derive the greatest benefit from chemotherapy. Notably, only about half of the patients reportedly received chemotherapy. This warrants further exploration, as it may reflect multifactorial barriers such as frailty, comorbidities, access disparities, or patient preference, all crucial to interpreting population-level survival patterns.

Another limitation that deserves mention is the lack of information on treatment delivery intensity and tolerability. Registry classifications based on intended regimens cannot capture dose reductions, treatment delays, or discontinuations—factors particularly relevant for FOLFIRINOX, often administered in modified forms (mFOLFIRINOX) to improve tolerability. Without these details, survival differences may reflect variations in patients’ ability to tolerate therapy as much as pharmacologic efficacy. This distinction between efficacy and real-world effectiveness represents a key dimension of confounding in observational oncology research.

In addition, the Engelke analysis predates the widespread adoption of biomarker-driven approaches now integral to pancreatic cancer management. Current European Society for Medical Oncology (ESMO), National Comprehensive Cancer Network (NCCN), and American Society of Clinical Oncology (ASCO) guidelines recommend routine germline and/or somatic testing to identify actionable subsets. For instance, patients with germline BRCA1/2 or PALB2 mutations may benefit more from platinum-containing regimens such as FOLFIRINOX and qualify for maintenance therapy with poly(ADP-ribose) polymerase (PARP) inhibitors, while those with microsatellite instability-high (MSI-H) tumors are candidates for immunotherapy. The absence of such molecular data limits contextualization of registry findings within the framework of precision oncology, where differential biology increasingly guides regimen selection.

Lastly, the generalizability of findings from a single regional registry warrants careful consideration. Differences in healthcare infrastructure, access, and treatment protocols across regions may influence survival outcomes and regimen selection. Expanding similar analyses to multicenter or national registries would provide a more comprehensive perspective and enhance external validity.

In conclusion, Engelke et al. have provided a valuable contribution by leveraging population-based data to explore real-world outcomes of systemic therapy for pancreatic cancer. With additional attention to confounding, missing data, treatment intensity, molecular stratification, proportional-hazards diagnostics, and pandemic-related effects, the study’s findings could be further strengthened and more confidently interpreted in everyday clinical practice.

Acknowledgments

None.

Footnote

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