Background: The use of complementary medicines (CAM) in the cancer population is higher than in the general population, with some studies estimating use as high as 70%.

At the Medicines Information Centre at a tertiary cancer centre we receive many enquiries regarding use and safety of CAM in combination with conventional cancer therapies (chemotherapy, radiotherapy and surgery). The aim of this project is to review the most common CAM enquiries with a focus on potential interactions or issues in the cancer population when used in combination with chemotherapy and/or radiotherapy, or pre-surgery.

Methods: An audit and review of CAM enquiries received at our centre over a 2 year period (July 2011 – June 2013) was conducted. The most commonly enquired about CAM were identified, and potential interactions or other issues with each CAM were described.

Results: A total of 462 CAM enquiries were received, involving a total of 330 different CAM. The 10 most commonly enquired about CAM (excluding vitamins and minerals) 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 of these CAM were found to have predicted or actual drug interactions or potential problems associated with their use when combined with chemotherapy and/or radiotherapy or when taken pre-surgery.

Conclusions: Whilst many CAM are safe when taken by themselves, there is significant potential for interactions or an increased risk of serious adverse effects when taken concurrently with conventional anticancer therapies such as chemotherapy and/or radiotherapy, or when taken pre-surgery. Human studies are lacking in this area and potential drug interactions often need to be predicted using in vitro data, making it difficult to quantify the clinical significance.