Safety and efficacy of vitamin B in cancer treatments: A systematic review

Background With rising rates of complementary and alternative medicine use, the exploration of complementary and alternative medicine integration into oncology treatments is becoming increasingly prevalent. Vitamin B compounds including B1, B2, B3, B5, B6, B9, and B12, have all been proposed as potentially beneficial in cancer prevention and treatment as well as side effect management; however, many studies contain contradicting evidence regarding the utility of B vitamins within oncology. Thus, the aim of this study was to evaluate the safety and efficacy of Vitamin B supplementation in the oncology setting. Design A systematic review was conducted following The Preferred Reporting Items for Systematic Reviews and Meta-Analyses—Scoping Reviews guidelines, using pre-specified search terms in PubMed to include randomized control trials, clinical trials, and case studies. Two reviewers independently reviewed titles, abstracts, and full-text articles for inclusion, with a third reviewer resolving conflicts, before the included articles underwent data extraction and quality appraisal. Data extraction was conducted through COVIDENCE, which was used to manage and track the data during the search process. Results Out of 694 articles initially identified, 25 articles met the inclusion criteria and were included in the review. Designs of the studies varied, including randomized control trials, clinical trials, and case/cohort studies. The impact of vitamin supplementation on cancer risk varied. Several studies found that certain B vitamin supplementation lowered cancer risk: B9 and B6 in nasopharyngeal carcinoma ( n = 1200 patients) and in pancreatic cancer ( n = 258 patients); B3 in hepatocellular carcinoma ( n = 494,860 patients); B6 in breast cancer ( n = 27,853 patients); and B9 in BRCA1-positive breast cancer ( n = 400 patients). However, some studies found that certain B vitamin supplementation increased the risk or negative outcomes of cancer: B6 during nasopharyngeal carcinoma treatment ( n = 592 patients); B6 in risk of hepatocellular carcinoma ( n = 494,860 patients); and B9 plasma levels in breast cancer ( n = 164 patients). Due to the many adverse effects that occur in cancer treatment, the effectiveness of Vitamin B supplementation in alleviating adverse effects was evaluated. In two separate studies, Vitamin B6 and Vitamin B12 supplementation with acupuncture was found to be effective as adjunct therapies aimed to reduce chemotherapy-induced peripheral neuropathy ( n = 23 patients and n = 104 patients, respectively). No significant findings were established regarding B vitamin supplementation in chemotherapy-induced hand-foot syndrome. Conclusions In this systematic review we concluded that B vitamin supplements have varying data regarding safety and efficacy in cancer. Taking into account the etiology of the cancer, the specific B-vitamin, and the presence of any side effects could help guide utilization of the data found in this review. Large, randomized controlled trials are needed to confirm these findings among various cancer diagnoses and stages. Given the widespread utilization of supplements, healthcare providers should understand the safety and efficacy of vitamin B supplementation to address questions that arise in caring for those with cancer.