Plant medicines, or herbal therapies, often called phyto-pharmaceuticals, are widely used as anti-cancer therapies, prescribed by integrative oncologists as well as self-prescribed by cancer patients.

Natural products have been major molecular structural resources for chemotherapy drug discovery for the last 50 years. Among the 520 new drugs approved in the US between 1983 and 1994, 157 were either natural products or derived from natural products. More than 60% of antibacterials and anticancer drugs originated from natural products.

There is evidence that specific phyto-pharmaceutical agents as well as whole herbal preparations can both harm and benefit cancer patients who are undergoing primary conventional cancer treatment. Therefore, knowledge of drug-herb interactions and of the growing literature in this field is crucial.