# The prevalence of clinically relevant herb-drug interactions between herbal products and anti-cancer therapy in older adults with cancer – A cross-sectional study

## TL;DR

This study finds that 4% of older cancer patients using herbal supplements experience potentially harmful interactions with their cancer treatments.

## Contribution

The study quantifies the prevalence of clinically relevant herb-drug interactions in older cancer patients undergoing anti-cancer therapy.

## Key findings

- Potentially relevant herb-drug interactions occurred in 4% of older cancer patients.
- Of these interactions, half were judged to be clinically relevant.
- Common herbs involved in interactions included red yeast rice, red coneflower, turmeric, and cannabis.

## Abstract

The use of herbal supplements is highly prevalent amongst people with cancer and may lead to clinically relevant herb-drug interactions (HDIs) with their anti-cancer treatment. As the number of older adults with cancer increases, the numbers of older adults with cancer that are at risk of a HDI with anti-cancer treatment increases as well.

The goal of this study was to establish the prevalence of potentially relevant HDIs in older adults who undergo anti-cancer treatment. Also, the overall use of herbal products in this population and possible associations with patient characteristics were investigated.

In this single center cross-sectional study patients aged ≥65 years were invited to participate if they underwent systemic anticancer treatment for a solid or hematological cancer. A questionnaire was developed to investigate the use of a selected set of frequently used herbs with known HDIs with regular medications. If a selected herb was used, the herb and oncological medication were assessed for potentially relevant HDIs. All potentially relevant HDIs were independently evaluated by two pharmacists on clinical relevance.

A total of 202 patients were included in the analysis. The mean age was 74 years and 54 % was male. The prevalence of potentially relevant HDIs was 4 % and overall herb use was 12 %. Thirteen potentially relevant HDIs were identified, of which 6 were judged to be clinically relevant. The clinically relevant HDIs concerned red yeast rice, red coneflower, turmeric, and cannabis. None of the patient characteristics were associated with overall herb use.

Potentially relevant HDIs between herbal supplements and oncological treatment occur in 4 % of older adults with cancer and half of these are clinically relevant. Healthcare providers should question patients with cancer on the use of herbal supplements and monitor for relevant HDI with the treatment given.