Complementary medicine use during cancer treatment and potential herb-drug interactions from a cross-sectional study in an academic centre

Abstract

Complementary medicine (CM) is used by one third to one half of cancer patients throughout the world. The objective of this study was to describe the prevalence of CM use and the potential for interactions with cancer treatments in an academic oncology centre. A cross-sectional study was conducted among patients undergoing current cancer treatment. Among 132 included patients, 56% had used CM since their cancer diagnosis and 45% were using CM during cancer treatment at the time of the survey. The main CM used were green tea (35%), herbal tea (35%), homeopathy (27%), dietary supplements (27%), and herbal medicines (27%). A small majority of patients (58%) spontaneously mentioned the use of CM to their oncologist. Of 42 identified combinations of concomitant use of biologically based CM and anticancer agents among the study patients, the potential for pharmacokinetic interactions of clinical relevance was not expected in 17 combinations (40%), hypothetical and deemed unlikely in 23 (55%), and of probable low clinical relevance in 2 (5%). Considering the high prevalence of CM use, active enquiries should be made by healthcare professionals to detect symptoms that may relate to CM tolerance and effects or that suggest interactions between CM and cancer treatments.

Figure 1

Patients’ recruitment procedure. CM = complementary medicine.

Figure 2

Patients’ perception of complementary medicine (CM). Results are expressed as the percentage of CM users agreeing more or less with questions that explore the belief in the efficacy of CM, their potential side effects, and their positive or negative impacts on cancer or its treatment. The last two items depict the extent to which patients deem themselves sufficiently informed about the benefits and risks associated with CM.

Figure 3

Communication about complementary medicine (CM). The first two bars indicate the percentage of participants asked by either the oncologists or the nursing staff if they were currently using CM. The third and fourth bars indicate the percentage of participants to whom oncologists or the nursing staff offered CM as part of care. The next two bars indicate the percentage of CM users who spontaneously mentioned their CM use to their oncologists or to the nursing staff. The last three bars indicate the reaction of oncologists to the disclosure of CM use by participants.

Figure 4

Table of potential pharmacokinetic interactions between herbal medicines and anticancer agents. Properties of herbal medicines in metabolic/transport pathways: Red = inhibition, green = induction, violet = controversial in references (inhibition and/or induction), blue: metabolic/transporter pathway, italic blue = metabolic pathway leading to a major active metabolite; 3A4 = cytochrome P450 3A4 (etc.); P-gp = P-glycoprotein; OCT = organic cation transport; DPD = dihydropyrimidine dehydrogenase. References used to build the table can be found online in Supplementary Data S3 and Supplementary Table S4.