When analyzing the toxicity of the rs1870377 variant in patients undergoing 5-fluorouracil-based chemotherapy for locally advanced rectal cancer, the VEGFR2 H472Q Q/Q genotype was associated with a higher risk of grade 3 mucositis of the proximal upper gastrointestinal tract in arm 2 of the study (induction and concomitant prolonged intravenous infusion of 5-FU with radiotherapy). The gene discussed is KDR; the disease is mucositis.