Colorectal cancer (CRC) is the third most common malignancy worldwide and the second most deadly cancer. Scientists have projected that by 2040, the prevalence will reach up to 3.2 million new cases annually due to population aging, disadvantageous diet transformations, and elevated exposure to risk factors. In the past decades, the five-year survival rate in colorectal cancer has significantly increased to 65% due to the development of an early endoscopic diagnosis and new chemotherapeutic approaches. Fluoropyrimidines, such as 5-fluorouracil or capecitabine, are commonly used to treat CRC. One of the most fundamental mechanisms of 5-FU is based on the inhibition of thymidylate synthase. This action is responsible for the therapeutic, but also toxic, effects of the drug. In this short review, we discuss the possible effects of vitamin D activity on colorectal cancer cells in relation to fluoropyrimidines. PubMed, Embase, and Web of Science databases were searched up to January 2022 for studies on vitamin D and 5-fluorouracil interaction mechanisms. Original studies, case reports, and review articles were included.
Vitamin D or its analogs target multiple biochemical pathways and modulate numerous pathophysiolo-gical mechanisms in the course of colon cancer, including those related to the pharmacological sites of fluoropyrimidines. However, the available data concerning vitamin D–fluoropyrimidine pharmacological interactions are limited, especially regarding patients suffering from colon cancer and being treated with fluoropyrimidines.