Prospective study of dihydropyrimidine dehydrogenase (DPD) activity and DPYD IVS14+1G>A mutation in patients developing FU-related toxicities: An updated analysis based on a ten-year recruitment across multiple French institutions

Abstract

2003 Background: Although DPD deficiency is a well established cause of severe FU-related toxicities, relationships between the depth of the deficiency and the intensity of the toxicity is still poorly documented. We analyzed DPD activity in a large population of patients with FU-related toxicities. Methods: Blood lymphocytes from 144 consecutive cancer patients having developed FU toxicities were collected from different French institutions between January 1993 and July 2004 (53 men, 91 women; mean age 57, extremes 31–94). DPD activity was measured with a radioenzymatic HPLC assay. The IVS14+1G>A mutation was analyzed in 102 patients (RFLP assay). Results: Grade 3–4 toxicity (WHO classification) was 64% for mucositis, 58% for neutropenia, 42% for thrombopenia, 19% for diarrhea and 14% for neurotoxicity. Toxicity led to patient death in 9 cases (8 women, 1 man). DPD activity ranged from 8 to 504 pmol/min/mg (mean 200, median 188, N=144). Nine patients had an activity < 50 pmol/min/mg (severe deficiency) and 19 had an activity between 50 and 100 pmol/min/mg (partial deficiency), thus accounting for a total of 19% deficient patients. The relative risk of developing grade 3–4 toxicity in DPD deficient patients relative to non-deficient patients was 7.69 for neurotoxicity (Fisher’s Exact test, p< 0.001), 2.93 for diarrhea (p<0.001), 1.73 for thrombopenia (p=0.01), 1.63 for mucositis (p<0.001) and 1.59 for neutropenia (p=0.005). The lower the DPD activity, the higher the mucositis, neutropenia or diarrhea grading (Spearman rank correlations, p< 0.03). Toxic deaths were significantly related to low DPD activity (Mann-Whitney p=0.002), with 7 patients out of 9 exhibiting a DPD deficiency. The DPYD mutation (wt/mut) was detected in only 2 patients; both exhibited a low DPD activity (44 and 142 pmol/min/mg) and developed grade 4 mucositis, neutropenia, thrombopenia and grade 3 neurotoxicity without toxic death. Conclusions: 1- Patients with normal DPD activity may develop FU-related toxicities. 2- The intensity of the FU toxicity is related to the severity of the DPD deficiency. No significant financial relationships to disclose.