© 1999 Cancer Research Campaign Article no. bjoc.1998.0098 Dihydropyrimidine dehydrogenase deficiency and

SummaryDihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme of 5-fluorouracil (5-FU) catabolism. We report lymphocytic DPD data concerning a group of 53 patients (23 men, 30 women, mean age 58, range 36–73), treated by 5-FU-based chemotherapy in different French institutions and who developed unanticipated 5-FU-related toxicity. Lymphocyte samples (standard collection procedure) were sent to us for DPD determination (biochemical method). Among the whole group of 53 patients, 19 had a significant DPD deficiency (DD; below 150 fmol min–1 mg–1 protein, i.e. less than 70% of the mean value observed from previous population study). There was a greater majority of women in the DD group (15 out of 19, 79%) compared with the remaining 34 patients (15 out of 34, 44%, P<0.014). Toxicity was often severe, leading to patient death in two cases (both women). The toxicity score (sum of WHO grading, theoritical range 0–20) was twice as high in patients with marked DD (below 100 pmol min–1 mg–1 protein, n = 11, mean score = 13.2) compared with patients with moderate DD (between 150 and 100 pmol min–1 mg–1 protein, n = 8, mean score = 6.8), P = 0.008. In the DD group, there was a high frequency of neurotoxic syndromes (7 out of 19, 37%). The two deceased patients both had severe neurotoxicity. The occurrence of cardiac toxicity was relatively rare (1 out of 19, 5%). These data suggest that women are particularly prone to DPD deficiency and allow a more precise definition of the DD toxicity profile.