Combined Therapies Increase Side Effects, Study Finds

Chemotherapy vials.

Adverse side effects increase with combined therapies, a new study has found. The study, presented at the Advanced Breast Cancer Fourth International Consensus Conference shows that combining targeted drugs with hormone therapy results in a significant increase in the risk of severe or life-threatening adverse events. Most of these side-effects are treatable, the researchers assert, but the information gained about them could improve patient quality of life and outcomes.

The research was presented by Dr. Matteo Lambertini, an oncologist at the Institut Jules Bordet in Belgium, and Professor Samuel Martel, an oncologist at CISSS Monteregie Centre/Hopital Charles-Lemoyne, Universite de Sherbrooke in Canada.

Until now, it was not known to what extent combined treatments contributed to more adverse side effects.

Previous studies have shown that advanced breast cancer can be better treated with combination therapies. Especially if the cancer is hormone receptor positive, which allows many hormone-targeting drugs to work to reduce cancer's spread.

In this study, researchers analyzed 8,529 patients who'd taken part in randomized, controlled clinical trials. The patients were all diagnosed with advanced hormone receptor-positive breast cancer and all had gone metastatic. Trials included popular hormone receptor targeting drugs. Some patients were also given combination therapies involving other commonly-used cancer inhibitors.

Patients who received the combination therapies had higher instances of adverse side-effects. This was especially true with certain agents such as anti-HER2, CDK4/6, and PI3K inhibitors. The most common adverse side-effects (graded 3 or 4) were fatigue, low white blood cell count, and diarrhea. The most side-effects were had with CDK4/6 inhibitors while most others doubled the risk.

"There are specific guidelines for the prevention and clinical management of side effects caused by targeted therapies. For example, recently, the prophylactic use of an alcohol-free dexamethasone mouthwash has been shown to reduce the incidence and severity of sore and inflamed mouth in patients treated with everolimus and exemestane, and it is likely to be considered as a new standard of care."



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