Drug interactions and oncological outcomes: a hidden adversary

Patients with cancer are at particularly high risk of drug-drug interactions, with approximately 30% of them being exposed to potentially dangerous drug-drug combinations. Yet the real impact of such interactions on oncology practice remains mostly unknown, partly because of the challenges associated with disentangling the effects of harmful interactions from expected side effects of therapy or disease-related symptoms. Recently, some studies have looked at how oncologic outcomes are influenced by drug-drug interactions. In this editorial, we discuss the drug combinations that should be avoided, such as, for example, capecitabine and proton-pump inhibitors, and how research should be conducted in this neglected but clinically relevant topic.