A new systematic review and meta-analysis published in BMC Cancer has now brought the weight of all available evidence to bear on that question, and its conclusions are both reassuring and subtly intriguing. Led by Mohammad Amouzadeh-Lichahi, Maryam Jafari, Nazila Sattari, Sara Zamani, Negin Letafatkar and Shahriar Ghodous of Guilan University of Medical Sciences in Rasht, Iran, the research team systematically searched PubMed, Scopus and Embase for observational studies published up to July 2026. Their exhaustive sweep of the literature identified twenty-seven reports that met their rigorous inclusion criteria, covering the use of oral contraceptive pills, menopausal hormone therapy, estrogen therapy alone, and combined estrogen–progestin therapy in relation to pancreatic cancer risk. By pooling adjusted effect estimates across studies with random-effects models, the team aimed to produce the most definitive statistical picture to date of how these hormonal exposures relate to one of oncology’s deadliest cancers.

The methodological machinery behind the analysis was considerable. The researchers followed PRISMA reporting guidelines and evaluated study quality using the Newcastle–Ottawa Scale, while the certainty of the resulting evidence was graded with the GRADE framework. Heterogeneity among studies was quantified with the I-squared statistic, and publication bias was probed with both Egger’s and Begg’s tests. Crucially, the team went beyond simple pooled estimates: they computed ninety-five percent prediction intervals, which indicate the range of effects that might plausibly be expected in a future study conducted in a new population, and they performed both linear and non-linear dose–response meta-analyses to test whether longer durations of hormone use translated into progressively altered risk. This layered approach matters because a pooled relative risk alone can mask enormous variability in what individual studies actually find.

The headline result for oral contraceptives was, in statistical terms, a null finding. Across twenty studies, women who had used the pill showed a pooled relative risk of pancreatic cancer of 0.99, with a ninety-five percent confidence interval spanning 0.86 to 1.14 — a range that comfortably includes no effect. The prediction interval was strikingly wide, stretching from 0.62 to 1.59, and heterogeneity between studies was substantial at 61.4 percent. The GRADE assessment rated this evidence as very low certainty. In plain language, the analysis found no overall association between oral contraceptive use and pancreatic cancer, but the underlying studies disagreed with one another enough that the true effect in any given population could conceivably fall anywhere between a meaningful reduction and a meaningful increase in risk.

Menopausal hormone therapy told a similar story. Drawing on eighteen studies, the pooled adjusted relative risk was 0.92, with a confidence interval of 0.79 to 1.06 that again crossed the threshold of no effect. Heterogeneity was even higher here, at 75.9 percent, and the prediction interval ranged from 0.54 to 1.56, once more signaling that results varied dramatically across populations and study designs. Estrogen therapy used alone, examined across six studies, yielded a pooled relative risk of 0.82 with a confidence interval of 0.63 to 1.07 — a point estimate hinting at a possible protective trend, but one that failed to reach statistical significance and was likewise graded as very-low-certainty evidence. For all three of these exposures, the adjusted analyses simply did not support a consistent link with pancreatic cancer.

The one exception emerged with estrogen–progestin therapy, the combined form of menopausal hormone therapy in which estrogen is paired with a progestin to protect the uterine lining. Across five studies, this regimen was associated with a modest but statistically robust inverse association: a pooled relative risk of 0.85, with a tight confidence interval of 0.78 to 0.93 and, remarkably, zero heterogeneity among the contributing studies. The prediction interval of 0.77 to 0.94 mirrored that consistency. This was the only finding in the adjusted analyses to achieve statistical significance, and it was graded as low-certainty evidence — a notch above the very-low ratings given to the other exposures, but still short of the certainty clinicians would want before drawing firm conclusions.

The biology behind such a signal is not far-fetched. Pancreatic ductal adenocarcinoma, the dominant form of the disease, expresses estrogen receptors and the G protein-coupled estrogen receptor, and experimental work has implicated estrogen signaling in pathways central to cancer cell behavior, including the PI3K/AKT and MAPK cascades, insulin-like growth factor signaling, and inflammatory and oxidative stress processes. Progestins, meanwhile, can modulate cell proliferation and differentiation. A modest protective effect of combined estrogen–progestin therapy is therefore biologically plausible, even if the observational nature of the evidence and the small number of contributing studies demand caution. Confounding by indication, differences in body mass index, smoking status, diabetes prevalence and other lifestyle factors across study populations could all shape the observed associations in ways that statistical adjustment cannot fully remove.

Indeed, the secondary crude analyses illustrated exactly how fragile such associations can be. When the researchers pooled unadjusted effect estimates instead of adjusted ones, they found substantially lower odds of pancreatic cancer among oral contraceptive users (an odds ratio of 0.70) and estrogen–progestin users (an odds ratio of 0.55). But both of these crude analyses were plagued by substantial heterogeneity and wide prediction intervals — the estrogen–progestin prediction interval stretched from 0.16 to 1.97 — suggesting that the apparent protection in crude data may partly reflect confounding by factors such as socioeconomic status, healthcare access, or healthier baseline profiles among hormone users rather than a genuine biological effect. The divergence between crude and adjusted results is a textbook demonstration of why observational hormone epidemiology is so treacherous.

The dose–response analyses added a further layer of nuance. Neither oral contraceptive use nor menopausal hormone therapy showed a significant linear relationship with pancreatic cancer risk per five-year increase in duration of use: the relative risks were 1.07 (p = 0.158) for the pill and 0.84 (p = 0.128) for menopausal hormone therapy. Non-linear models likewise failed to identify any significant threshold or U-shaped pattern. In other words, there was no evidence that taking hormones for longer periods progressively shifted risk in either direction, which weakens the case for a strong causal relationship and suggests that any real effects, if they exist, are likely to be modest and context-dependent.

The authors’ conclusions are measured and appropriately cautious. The adjusted evidence did not show a consistent association between oral contraceptive, menopausal hormone therapy, or estrogen therapy use and pancreatic cancer risk, and although estrogen–progestin therapy was linked to a modest reduction in risk, that finding rests on low-certainty observational evidence from only five studies. The wide prediction intervals for oral contraceptives and menopausal hormone therapy indicate that associations may vary across populations and settings, and the team explicitly calls for further large prospective studies to clarify the long-term hormonal effects on pancreatic carcinogenesis. For the millions of women weighing the risks and benefits of hormonal medications, the practical takeaway is largely reassuring: nothing in this comprehensive synthesis suggests that these widely used therapies meaningfully raise the risk of pancreatic cancer. And for researchers, the modest inverse signal from combined therapy offers a tantalizing, testable hypothesis — one that could ultimately illuminate how estrogen and progestin signaling shapes one of medicine’s most lethal tumors.

Subject of Research: The association between oral contraceptive and menopausal hormone therapy use and pancreatic cancer risk

Article Title: Oral contraceptive and menopausal hormone therapy use and risk of pancreatic cancer: a systematic review, meta-analysis, and dose–response analysis

Article References: Oral contraceptive and menopausal hormone therapy use and risk of pancreatic cancer: a systematic review, meta-analysis, and dose–response analysis. (n.d.). https://doi.org/10.1186/s12885-026-16902-6

Image Credits: AI Generated

DOI: 10.1186/s12885-026-16902-6

Keywords: pancreatic cancer, oral contraceptives, menopausal hormone therapy, estrogen therapy, estrogen–progestin therapy, meta-analysis, systematic review, dose–response analysis, observational studies, exogenous hormones, BMC Cancer, cancer epidemiology