A systematic review of vitamin D supplementation in oncology: chance of science or effectiveness?

Background: Vitamin D (VD) supplementation has increased considerably in the last decade, whether for the prevention or treatment of numerous diseases, including bone, cardiovascular, endocrine, neurologic, psychological, respiratory, infectious, or oncological. The primary objective of this scoping review was to examine and synthesize the scientific evidence on the role of VD in all-type cancer patients undergoing adjuvant and neoadjuvant therapy with chemotherapy (CT) or radiotherapy (RT), namely in improving side effects. Methods: This review was conducted by selecting papers from the CINAHL, Scopus and PubMed databases based on the descriptor terms mesh and title/abstract, taking into consideration the defined inclusion and exclusion criteria, following the PRISMA-ScR (PRISMA extension for scoping reviews) statement. Results: A total of 758 papers were identified in different databases during this review. However, using the inclusion and exclusion criteria, only five publications made up the final sample of the study. The studies included heterogeneous study methodologies, objectives, cancer diagnosis, as well as methods to assess body composition, which makes it difficult to compare them. Based on the analyzed studies, associations were found between bone density and VD in patients who underwent preoperative chemoradiotherapy (CRT). In patients with non-small-cell lung cancer receiving CT, some of the side effects associated with the treatment were attenuated and reduced. In addition, another of the studies analyzed found that VD deficiency (VDD) has been associated with increased peripheral neuropathy (PN) induced by CT in the treatment of breast cancer. VD supplementation was found to be safe and effective. Conclusions: In this scoping review, VD is highlighted as a crucial factor in preventing the side effects of neoadjuvant RT or CT, as well as treating other treatmentrelated health conditions, such as osteoporosis, as well as ameliorating the side effects (nausea, vomiting, fatigue) associated with aggressive CT and RT.