5-Fluorouracil (5-FU) and its prodrug capecitabine are widely used and generally well-tolerated chemotherapeutic agents. Although leucovorin, a derivative of folic acid, is routinely used to potentiate the effect of 5-FU, there seems to be little to no awareness about a similar interplay between capecitabine and folic acid, a commonly used supplement. This study presents a case in which a high concentration of folic acid led to fatal capecitabine-related toxicity, with the aim to raise awareness on the interaction between folic acid supplementation and 5-FU/capecitabine treatment toxicity.

(BELG J MED ONCOL 2022;16(2):74–8)