ABSTRACT
PURPOSE: Vitamin A and its derivatives positively influence the differentiation of epithelia and other tissues and prevent the proliferation of preneoplastic and neoplastic cells. Vitamin A is therefore taken into account as a potential supporting factor in cancer therapy. METHODS: In November 2020, a systematic search was conducted searching five electronic databases (EMBASE, Cochrane, PsycINFO, CINAHL and Medline) to find studies looking at the effects of using vitamin A as a complementary therapy for cancer patients. From all 12,823 search results, 9 publications referring to 9 studies with 4296 patients were included in this systematic review. RESULTS: The patients treated with vitamin A were diagnosed with various cancers and stages. Outcome variables were overall survival of cancer, progression-free survival, occurrence of second primary tumours and recurrences, improvement of chronic radiation-induced proctopathy and side effects of vitamin A. For the most part, the studies had a limited methodological quality. In summary, it can be said that due to the methodological deficiencies of the studies, no concrete statement can be made regarding the prolongation of overall survival and progression-free survival. There is also no evidence of the benefit of vitamin A in the treatment of chronic radiation-induced proctopathy, which can be attributed to methodological deficiencies in the study, as well. In the studies that report on side effects, it becomes clear that side effects, such as mucocutaneous symptoms, temporary increase in liver enzymes and gastrointestinal side effects occur more frequently in the group with vitamin A intervention. CONCLUSION: The limited interpretability of the results due to the methodological deficiencies of the included studies does not allow a final statement on the benefits of vitamin A as a complementary treatment for cancer patients.
