The study, which included 23,000 people, aimed to understand how everyday medications — such as blood pressure, cholesterol-lowering, and heartburn medications — interact with cancer treatments.
The results showed that proton pump inhibitors (PPIs), used to treat indigestion and heartburn, were associated with lower overall survival rates in breast cancer patients and a 36% increased risk of severe treatment-related side effects.
It is believed that these drugs may interfere with the body's immune responses or change the way cancer drugs are absorbed and metabolized, although more research is needed to confirm this.
The study also found that some heart and blood pressure medications — such as beta-blockers, ACE inhibitors, angiotensin receptor blockers and calcium channel blockers — were associated with higher rates of severe side effects, but did not significantly affect survival rates.
Other commonly used drugs, such as statins for treating high cholesterol and metformin for treating diabetes, have not shown any significant effects on survival rates or the occurrence of side effects, which is reassuring regarding their safety.
The study's findings were based on an analysis of 19 major clinical trials sponsored by global pharmaceutical companies, including Lilly, Pfizer and Roche, and are believed to be the largest and most comprehensive study of its kind in the world.
Dr. Natansh Modi, lead author from the University of South Australia and Flinders University, said: "The findings reveal a complex relationship between commonly prescribed drugs and cancer treatment outcomes. Many women with breast cancer also suffer from chronic conditions such as high blood pressure, diabetes, or acid reflux, which means they take multiple medications at once. Our findings do not mean stopping non-cancer drugs, but they do underscore the importance of doctors regularly reviewing patients' medications."
Associate Professor Ashley Hopkins of Flinders University noted: "Patients taking proton pump inhibitors need special attention in oncology centers. This does not mean stopping medication without medical advice, but doctors should assess the actual need for these drugs and review the potential risks."
The researchers stressed that the study highlights the need for a more holistic approach to breast cancer management that takes into account all the medications a patient is taking, and called for follow-up studies to explore the biological reasons behind drug interactions and to develop clinical guidelines for the safe combination of drugs during treatment.
The study was published in the journal Cancer Medicine.
