A large international study has found troubling associations between widely used medications and breast cancer treatment outcomes. Conducted by the University of South Australia and Flinders University, the research involved 23,000 people and examined the impact of common drugs, including blood pressure tablets, cholesterol-lowering medications, and heartburn treatments, on patients with breast cancer.
The study identified that proton pump inhibitors (PPIs), typically used for indigestion and heartburn, were linked to poorer overall survival rates among breast cancer patients. Furthermore, those using PPIs faced a 36% higher risk of severe side effects related to their treatment. Researchers suggest that PPIs might disrupt the body’s immune responses or alter the absorption and metabolism of cancer therapies, although more research is needed to clarify these mechanisms.
Link Between Common Heart Medications and Side Effects
In addition to PPIs, the study found that other medications, such as beta-blockers, ACE inhibitors, angiotensin receptor blockers, and calcium-channel blockers—prescribed frequently for heart disease and hypertension—were also associated with increased rates of severe side effects. Notably, these medications did not appear to impact overall survival. In contrast, statins and metformin, commonly utilized to manage high cholesterol and diabetes, respectively, showed no significant effects on survival or adverse events, providing some reassurance regarding their safety.
The findings, published in the journal Cancer Medicine, emerge from an extensive analysis of data from 19 major clinical trials sponsored by pharmaceutical companies including Lilly, Pfizer, and Roche. This research is considered one of the largest and most comprehensive studies of its kind globally.
Lead author Dr. Natansh Modi from UniSA and Flinders University emphasized the complex relationship between commonly prescribed medications and cancer outcomes. “Many women with breast cancer are also managing other chronic conditions such as high blood pressure, diabetes, or acid reflux, meaning they are often taking multiple drugs at once,” he stated. Dr. Modi highlighted that while the findings do not suggest patients should discontinue their non-cancer medications, they underscore the necessity for medical professionals to regularly review patients’ medication regimens.
Recommendations for Patient Care
Senior author Associate Professor Ashley Hopkins from Flinders University noted that patients using PPIs in oncology settings should receive particular attention. “It doesn’t mean that patients should cease their reflux medication without medical advice, but clinicians should be alert to potential risks and review whether PPIs are genuinely needed,” he advised.
The researchers argue for a more holistic approach to breast cancer treatment, one that considers all medications a patient is taking. They are calling for further studies to investigate the biological reasons behind the observed interactions and to establish clinical guidelines for the safe co-prescription of these medications during cancer therapy.
The implications of this research are significant, as they highlight the need for tailored treatment plans in breast cancer management, ensuring that patients receive comprehensive care that takes into account their multiple health conditions.
For detailed findings, refer to the study: Natansh D. Modi et al, “Associations of Commonly Used Concomitant Medications With Survival and Adverse Event Outcomes in Breast Cancer,” Cancer Medicine (2025). DOI: 10.1002/cam4.71320.
