RESUMO
Cisplatin (CDDP) combined with radiotherapy (RT) is employed in head and neck squamous cell carcinoma (HNSCC) with variable toxicities and clinical response. Glutathione S-transferases (GSTs) participate in CDDP excretion from cells, and genes encoding GSTs, GSTM1, GSTT1and GSTP1, are polymorphic in humans. This prospective study aimed to evaluate the roles of GSTM1, GSTT1, and GSTP1 Ile105Val polymorphisms in outcomes of HNSCC patients treated with CDDP chemoradiation. Ninety patients were genotyped by multiplex PCR. Urinary CDDP measurements were performed by HPLC. Treatment side effects and response were analysed by conventional criteria. Patients with GSTT1 genes showed 7.23- and 5.37-fold higher likelihood of presenting vomiting and ototoxicity, lower glomerular filtration rate (GFR), and lower elimination of CDDP in urine relative to patients with deleted genes. Patients harbouring the GSTP1 IleVal or ValVal genotypes showed 4.28-fold higher likelihood of presenting grade 2 or 3 vomiting and lower GFR with treatment than those harbouring the IleIle genotype. In multivariate Cox analysis, patients with the GSTP1 105ValVal genotype had 3.87 more chance of presenting disease progression than those with the IleIle or IleVal genotype (p < 0.01). Our findings provide preliminary evidence that inherited abnormalities in CDDP metabolism, related to GSTT1 and GSTP1 Ile105Val polymorphisms, alter outcomes of HNSCC patients treated with CDDP and RT.
