ABCB1, CYP3A5*3, and CYP3A4*1B SNPs and risk of toxicity with sunitinib treatment for mRCC.

Abstract

485 Background: Currently there are no biomarkers to predict either toxicity or activity of targeted therapy in mRCC. The aim of this study was to correlate single nucleotide polymorphisms (SNPs) of genes encoding for efflux transporters and metabolizing enzymes with sunitinib toxicity in metastatic renal cell carcinoma (mRCC) patients (pts). Methods: We conducted an observational, retrospective analysis of 60 Caucasian pts who received sunitinib for mRCC from 2 Italian institutions. Correlation between adverse events (AE, according to CTCAE v.4.0) and 4 polymorphisms in 3 genes (ABCB1 [1236C>T, 3435C>T], CYP3A5*3 6986A>G, CYP3A4*1B-392A>G) was analyzed. SNPs were detected in blood samples using pyrosequencing technique. Association between SNPs and toxicities was evaluated using the Chi Square test. Results: 60pts (median age: 61 years; male: 63.3%) with mRCC (clear cell: 85%, other histologies: 15%) were treated with sunitinib (83.3% as first-line). The most common AE (any-grade) reported were: hypertension (85%), asthenia (83.3%), hypothyroidism (65%), anemia (61.6%), nausea/vomiting (60%), stomatitis (58.3%), diarrhoea (48.3%), neutropenia (48.3%), thrombocytopenia (46.7%), leukopenia (46.7%), hypertriglyceridemia (45%), hyperglycaemia (38.4%), hypercholesterolemia (35%), and hand-foot syndrome (35%). Treatment was discontinued and sunitinib dose was reduced due to AE in 28.3% and 61.7% of pts, respectively. The G/A-variant in CYP3A5*3 was associated with thrombocytopenia (any grade, p=0.03); homozygous C/C alleles in ABCB1 1236C>T significantly correlated with leukopenia (any grade, p=0.01), while the C/C genotype in ABCB1 3435C>T was associated with hypertension (grade≥3, p=0.05); hypertriglyceridemia showed a trend towards increased prevalence in the presence of the C allele (grade≥3, p=0.08). Conclusions: Polymorphisms in ABCB1 and CYP3A5*3 are predictive of toxicity, as hypertension, leukopenia, and thrombocytopenia in pts with mRCC treated with sunitinib. This analysis could support the selection of the more appropriate drug to the individual patient.