When Nature Meets Oncology: Unraveling Herb–Drug Interactions in Cancer Therapy

Natural product (NP) use by patients alongside their conventional cancer therapies is ubiquitous. This common, yet often hidden, practice can potentially contribute to significant patient harm, given the narrow therapeutic window of most anticancer drugs. This review takes on this challenge directly, moving past theoretical concerns to summarize current clinical evidence on interactions between widely used NPs and modern cancer treatments, including chemotherapy, targeted therapy, and immunotherapy. We break down the key pharmacokinetic (PK) mechanisms, such as the disruption of cytochrome P450 enzymes, and the pharmacodynamic (PD) effects that can either help or hinder treatment. By examining clinically important examples, we highlight how NPs can alter the effectiveness of anticancer medications. Lack of reliable safety information for NPs along with widespread use of these products by patient populations has the potential to impact clinical care and patient outcomes significantly, frequently causing harm. We advocate for improved patient-provider communication and additional evidence based research to address this gap in literature.