Complementary and alternative medicine (CAM) treatments are popular among cancer patients; some estimates indicate that as many as half of all patients use some sort of these therapies before and during treatment.
However, some of these therapies could alter the effect of anticancer treatment and may be associated with drug-drug interactions (DDIs), according to two new studies that will be presented at the forthcoming European Society for Medical Oncology (ESMO) 2018 Congress, to be held in Munich, Germany, on October 19-23.
The first study found that 60% of patients recognized that the information they had on the safety of CAM treatments was insufficient but were not very concerned about potential risks.
In the second study, the authors found that among patients undergoing chemotherapy or treatment with tyrosine kinase inhibitors (TKIs), 18% reported major DDIs during the study period. Of these DDIs, which required pharmacist interventions, 29% were associated with CAM treatments.
Commenting on the new studies for ESMO, Markus Joerger, MD, of Cantonal Hospital in St. Gallen, Switzerland, explained that the perception that all CAM treatments are low risk is a big problem. "Patients tend to believe that supplements or herbs are generally safe, but they are not without risk," he said in a statement. "In daily practice, if you don't know what your patient is taking as alternative medicine, the risk of drug-drug interactions can significantly increase and have an impact on clinical outcomes."
Information on Risks Lacking
In the first study, a team from the University Hospital Mannheim, Germany, conducted a survey to determine the use of CAM among 125 patients undergoing treatment at a sarcoma center. The patients had biopsy-proven sarcoma, gastrointestinal stromal tumors (GIST), and desmoid tumors.
The team used a structured cross-sectional questionnaire that had been previously validated in melanoma and breast cancer patients.
In this survey, CAM covered a broad array of modalities, including vitamin or mineral supplements, Chinese or healing herbs, homeopathy, acupuncture, meditation, yoga, and Tai Chi. Also included were changes in dietary habits, such as switching to a ketogenic or vegan diet.
A total of 51% of participants had used alternative modalities during the course of their lifetime; 15% only used them after their cancer diagnosis in parallel with standard treatments. The authors note that the cancer diagnosis appeared to have stimulated an interest in CAM treatments in 44% of participants.
The main reasons given for the interest in and use of CAM were to boost the immune system (78%), to help the patient feel better (76%), to help the patient cope with cancer treatment (45%), to reduce stress (53%), and to reduce symptoms or side effects (36%).
Study supervisor Peter Hohenberger, MD, from the University Hospital Mannheim, noted that patients were selective in their choice of CAM treatments.
"What we found is that vitamins and minerals are very popular, but patients take them specifically rather than using multivitamin supplements," he said. "Vitamin D is in the leading position, followed by selenium plus zinc, vitamin C, and interest in vitamin B17 is emerging."
Almost a third (30%) of patients reported taking vitamin and mineral supplements, especially vitamin D. Other popular modalities were traditional Chinese medicine (32%) and homeopathic medicine (32%).
The team also found that more than half (60%) of patients in the survey were aware that they had insufficient information about safety issues regarding CAM therapies, but they appeared to have little concern regarding potential risks.
Oncologists were not the primary source of information when it came to investigating CAM modalities. "When we looked at the sources of information on nonconventional practices, oncologists represented only 7%," said Hohenberger. "In our study, patients mentioned repetitively that they were positively surprised about our interest in their use of CAMs."
The main source of information about CAM was the Internet and other media (43%), friends (15%), and healthcare professionals (14%). Conversely, when it came to investigating information about the side effects of cancer therapies or how to handle them, almost half of patients asked their oncologist.
Commenting on the study, Joerger emphasized that oncologists should try to preserve their role as a primary source of information for their patients.
"Although we must not demonize the Internet or other sources of information, getting information outside the clinical setting can often be misleading," said Joerger. "Patients have to realize that they can discuss any health-related choices with their oncologist and be advised on different options when they wish to reduce stress related to cancer treatment or, more in general, to feel better."
DDIs Include CAM
In the second study, Audrey Bellesoeur, MD, of the University Paris Descartes, France, and colleagues investigated potential drug interactions between cancer treatment and CAM.
The team conducted a retrospective review of 202 sarcoma patients who were beginning chemotherapy (doxorubicin, ifosfamide, gemcitabine, trabectedin-based or other type) or treatment with a TKI.
The cohort included 122 patients with soft-tissue sarcoma and 80 patients with bone sarcoma. Of these patients, 86% were undergoing treatment with chemotherapy, and 14% with a TKI. Patients received a median of three drugs; 65 patients (32%) received at least five drugs.
In addition, 34 patients (17%) reported using CAM. Factors associated with CAM use included marital status (P = .003) and ethnic origin (P = .03).
The investigators identifed 37 major potential interactions. On univariate analysis, the number of drugs (P < .001), performance status (P = .04), pain (P = .002), and use of antidepressants (P < .001), proton pump inhibitors (PPIs) (P < .001), and TKIs (P < .001) were identified as risk factors for DDIs.
The use of TKIs, PPIs, and antidepressants remained significant in multivariate analysis (P < .02).
A pharmacist performed 157 medication reconciliations and recommended 71 interventions for 59 patients (24%). These included discontinuing 34 drugs, replacing 16 others, adjusting doses in two cases, and monitoring 19 others. Pharmacist interventions occurred more frequently for patients treated with TKIs than for those receiving chemotherapy (63% vs 17%; P < .001); 29% of these interventions involved CAM.
"In our review, 29% of drug-drug interactions requiring pharmacist interventions were associated with complementary alternative medicines," Bellesoeur said in a statement. "Risks of interactions with nonconventional drugs are the same as for other co-medications, mainly increased toxicity and loss of efficacy of anticancer treatments."
However, she pointed out that there is little information on the composition of these products and their risk of toxicity or interaction when used in combination with other agents.
Joerger feels that characterizing the risk for DDIs will be increasingly relevant in the future. "Since more options of care are available, patients are receiving more and more co-medications, but they are still not routinely checked for drug-drug interactions," he said. "Medical review by a clinical pharmacist can certainly be an effective strategy to avoid or limit them as the study showed."
Dr Hohenberger's study was funded by EU-FP7 EUROSARC. Dr Bellesoeur's study did not receive any funding. The authors have disclosed no relevant financial relationships.
European Society for Medical Oncology (ESMO) 2018 Congress. Abstracts 1655P_PR and 1632P_PR, to be presented October 22, 2018.
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