Herb and Supplement Use During Cancer Treatment May Cause Drug Interactions That Could Be Harmful for Patients


Patients with prostate and breast cancer may be unknowingly putting themselves at risk while taking herbs and supplements during chemotherapy and should consult their medical team before using them, according to an expert.

The use of herbs and supplements not regulated by the Food and Drug Administration (FDA) during and after treatment with chemotherapy among patients with prostate or breast cancer is prevalent, and may put patients at risk of potential negative drug interactions that could be harmful, according to data published in Cancer.

“I think physicians, oncologists in particular, have a lot of concerns about potential drug-drug interactions — and, of course, that also relates to herbs and supplements,” lead study author Dr. Richard Lee, director of the Supportive and Integrative Oncology Program at University Hospitals Seidman Cancer Center in Cleveland, Ohio, said in an interview with CURE®. “I've done a survey where we looked at a national survey of oncologists, and one of their major concerns that they reported in that article was potential interactions. And so, we wanted to understand to what degree this may actually exist. That's why we did this pilot study; to see if this is really an issue among patients undergoing treatment of herb-supplement interactions.”

Patients with either prostate or breast cancer who had completed a course of systemic chemotherapy were recruited from two cancer clinics in the Chicago area. Patients were then interviewed over the phone from December 2008 to December 2009.

A total of 67 patients (median age, 55 years; breast cancer diagnosis, 87%) were included in the evaluation. Prior to starting chemotherapy, 49% of patients used herbs and supplements, which then increased to 51% during and 66% after treatment was over.

More than half (56%) of the patients reported taking herbs and supplements due to cancer-related reasons. Most of the patients (79%) using herbs and supplements said they had discussed it with at least one member of their care team and that most of the discussions were started by a physician (56%).

The data demonstrated that there were 1,747 potential drug-drug interactions throughout the study period. Prescription medication use was most associated with possible drug-drug interactions (70%), with herbs and supplements accounting for the second most (56%). The highest risk of an interaction was during chemotherapy (90%) and declined after chemotherapy (73%) was complete. Half of the potential drug interactions were moderate (54%) and 38% were major. Overall, 84% of patients were at risk for a major potential drug interaction.

In this study, herbs and supplements commonly associated with the highest severity of potential drug interactions were multivitamins, vitamin D, E and C, glucosamine and magnesium.

“Some of the (potential drug interactions) that have been documented is that herbs and supplements, such as St. John's wort or green tea, can actually interfere (with) certain types of chemotherapy, (making) them less effective, or may change the metabolism. So, it puts (patients) at risk for changing how the chemotherapy might either work or potentially cause more side effects,” Lee said.

Moreover, herbs and supplements such as green tea and Kava can be toxic to the liver, according to Lee. Additionally, Lee said, there are concerns that herbs and supplements thought to have antioxidant effects may interfere with the effectiveness of the chemotherapy someone is receiving.

When the study authors asked the patients if they thought the herbs and supplements worked, 59% said yes and 37% said maybe. Most of the patients (79%) said they were not concerned about possible side effects. When asked hypothetically if they would stop taking an herb or supplement because it might cause an interaction with their cancer treatment, more than half (69%) said they would and 24% said they would discuss it more with their physician.

“A patient should definitely talk to their medical team about the herbs and supplements that they're taking, they're just as important to relay to your medical team as any prescriptions or over counter medicines that they might be taking,” Lee said.

Some people, according to Lee, believe that herbs and supplements are natural and safe. However, Lee said, experts don’t know how safe they are.

Further research, Lee explained, is needed to assess the risks and benefits of the use of herbs and supplements and what potential harms drug interactions could lead to in patients with cancer.

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