Potential issues with complementary medicines commonly used in the cancer population: A retrospective review of a tertiary cancer center's experience.

AIM: Complementary medicine (CAM) use in the cancer population is higher than the general population: some studies estimate up to 70%. Our Medicines Information Centre, in a tertiary cancer institution, receives many enquiries regarding use and safety of CAM with conventional cancer therapies (chemotherapy, radiotherapy and surgery). This project aims to review the CAM most commonly enquired about with an emphasis on potential interactions with conventional cancer therapies.

METHODS: An audit and review of CAM enquiries from patients or medical professionals at our center, over a 2-year period (July 2011-June 2013), was conducted. The most commonly enquired about CAM, excluding vitamins and minerals, were identified, reviewed and potential interactions described.

RESULTS: Enquiries were received from 462 patients involving 330 different CAMs. The 10 CAMs most commonly enquired about were fish oil (3.54%), turmeric (3.24%), coenzyme Q10 (2.63%), milk thistle (2.44%), green tea (2.38%), ginger (2.14%), lactobacillus (2.08%), licorice (1.83%), astragalus (1.77%) and reishi mushroom (1.59%). All were found to have predicted or potential drug interactions or therapeutic issues when combined with conventional therapies. Human studies are lacking and potential drug interactions are often predicted using in vitro or in vivo animal data.

CONCLUSIONS: While many CAMs may be safe when taken by themselves, there is theoretically a potential for interactions and/or increased risk of serious adverse effects when taken concurrently with conventional anticancer therapies. The paucity of human data implies that their clinical significance is difficult to quantify and hence caution is required.