Some common meds linked to adverse breast cancer outcomes: study

Common medications taken by millions of Australians have been linked to adverse outcomes for breast cancer patients, a new study has found.

The study revealed a complex relationship between commonly prescribed medications and cancer outcomes but is not advocating anyone should stop taking medications without medical advice.

Researchers from the University of South Australia and Flinders University set out to investigate how everyday items such as blood pressure pills, cholesterol-lowering drugs, and heartburn medication, may interact with cancer therapies.

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They found that proton pump inhibitors (PPIs) used to treat indigestion and heartburn were associated with poorer overall survival for breast cancer patients, and a 36 per cent higher risk of severe, treatment-associated side effects.

Researchers believe PPIs could interfere with the body's immune responses, or change how the body reacts to cancer drugs, though they note further investigation is needed.

The study, published in Cancer Medicine, also found that drugs commonly prescribed for heart disease or hypertension, such as beta-blockers, ACE inhibitors, angiotensin receptor blockers, and calcium-channel blockers, were linked to higher rates of severe side-effects from breast cancer treatment - but did not appear to affect overall survival rates.

Drugs such as statins and metformin, used to manage high cholesterol and diabetes respectively, showed no significant impacts on either survival or side effects.

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The data was based on 19 major clinical trials involving 23,000 people, sponsored by pharmaceutical companies including Lilly, Pfizer and Roche, and is believed to be the largest and most comprehensive analysis of its kind in the world.

Lead author Dr Natansh Modi, from UniSA and Flinders University, said the findings revealed a 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," Modi said.

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"Our results don't suggest that people should stop taking their non-cancer medicines, but it underlines how important it is for doctors to regularly review patient medications because people are living longer and managing multiple health issues."

Corresponding senior author, Flinders University Associate Professor Ashley Hopkins, said the findings show that patients taking PPIs in cancer treatment settings warranted closer attention in particular.

"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 said.

The researchers said the study highlighted the need for a more holistic approach to breast cancer management that considered all medications a patient was taking.

The authors have also called for follow-up studies to explore the biological reasons behind the observed drug interactions and to develop clinical guidelines for the safe co-prescription of these medicines during cancer therapy.

This year, the government estimates more than 20,000 people will be diagnosed with breast cancer, of which 3353 are predicted to die.

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