If you speak with patients about the OTC medications or supplements they take, there is a good chance that many have tried or are currently using some form of probiotic. I have found this to be especially true of oncology patients seeking to complement their diet or those who are trying alternative medicines after numerous regimens of chemotherapy. As is evident by their strong presence in the media, probiotic use has dramatically increased over the last decade. Advertisements in magazines, pharmacies, and supermarkets and on television have boosted their popularity in both the public and healthcare communities.

Several hospitals have instituted a policy by which all admitted patients receiving antibiotics are automatically placed on a formulary probiotic medication. Patients and the occasional healthcare professional can potentially fall into the mindset that all “natural products,” including probiotics, are automatically safe because they can be purchased without a prescription. Providers should ask simple yet important questions of their oncology patients in order to appropriately monitor them for potential adverse side effects while using probiotics.

As per the Food and Agricultural Organization of the World Health Organization, probiotics are “live microorganisms that when administered in adequate amounts confer a health benefit on the host.” Probiotic products include bacteria such as Lactobacillus, Bifidobacterium, and Streptococcus and the yeast Saccharomyces. Numerous preparations are available as OTC capsules or tablets as well as dietary supplements within yogurts and other products. There is some clinical data to support the preventative and therapeutic use of probiotics in several clinical conditions. However, the safety profile of each probiotic in cancer patients remains unclear. In several retrospective analyses, evidence of bacteremia and fungemia was present in cancer patients taking probiotics, although the exact risk is unknown. Since the cause of such positive blood cultures is commonly polymicrobial, calculating an exact risk is complicated by a multitude of factors that are a direct result of the patient’s cancer. 

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Additional data have found serious adverse events such as pneumonia and endocarditis in “immunosuppressed” patients. These patients include those with conditions such as HIV, diabetes, and those receiving medical treatment posttransplantation. Although cancer patients were not strictly included in these studies, the research helps raise the question whether patients with weakened immune systems are consistently at a higher risk for adverse effects associated with probiotic use. In contrast to this adverse safety data, some studies show the benefits of probiotic use with minimal side effects in postsurgical colorectal cancer patients. Other studies indicate that probiotics can reduce radiation-induced diarrhea in patients receiving radiation therapy to the abdomen or pelvis.

Clearly, there is conflicting data on the risks and benefits of probiotics in patients with cancer. Additional prospective clinical trials are needed, as is heightened provider awareness of probiotic use in oncology patients. Oncology patients should be asked if they use these products at home and if so, the specific type, frequency, and when they take it in relationship to their other medications should be recorded. Many of the probiotic products in yogurt contain potassium, calcium, and other vitamins that could theoretically cause drug-drug interactions if ingested in sufficient quantities. In addition, bacteremia or fungemia secondary to probiotic use should be considered in the differential diagnosis of a cancer patient being admitted to a hospital to rule out infection.

If the patient has been recently admitted to a hospital, contact the hospital and inquire if they follow a policy where probiotics are automatically ordered for patients receiving antibiotics. This policy would not only impact the patient’s hospital stay, but it could also cause the patient to be discharged on probiotics and inadvertently continue them without appropriate medical oversight because they are available OTC. Asking some of these questions may sound arbitrary and time-consuming, but they can help you gather vital information about your cancer patient’s health.

  • Do you recommend the use of probiotics in your oncology patients and if so, which ones and at what frequency?
  • Have you ever observed an adverse effect from an oncology patient using probiotics, and if so what were the effects and clinical outcomes?

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