Molecular predictors of clinical outcome in differentiated thyroid cancer: prognostic significance of germline polymorphisms of VEGF-A, VEGFR-2, and PDGFR-?.

Angiogenesis is crucial for cancer progression and its efficiency may affect disease evolution, and therefore clinical outcome. Given that cancer-related vessel formation relies on the host angiogenic machinery, individual genetic variability affecting physiological angiogenesis may impact on cancer prognosis. Function of angiogenesis-regulating genes may be affected from single nucleotide polymorphisms (SNPs) through the modulation of gene-expression. Prognostic stratification of differentiated thyroid cancer (DTC) is still suboptimal as no effective tools are available for identifying patients with persistent/recurrent disease after thyroid ablation. Our objective was to evaluate germline SNPs of VEGF-A, VEGFR-2, and PDGFR-?, as prognostic markers of clinical outcome in DTC. Multicenter retrospective study including consecutive DTC patients subjected to post-surgical follow-up. Eight angiogenesis-related SNPs were included in the analysis: -2578 C>A (rs699947), -460 T>C (rs833061), +405 G>C (rs2010963), and +936 C>T (rs3025039) for the VEGF-A gene; +1192 C>T (rs2305948) and +1719 T>A (rs1870377) for the VEGFR-2 gene; -1309 G>A (rs6554162) and -635 G>T (rs1800810) for the PDGFR-? gene. Genotyping was performed by means of TaqMan protocol. Prognostic outcome was categorized as persistent structural disease, recurrent structural disease, and no evidence of disease at last follow-up. Genotypes were analyzed as three-group categorical variable and according to the dominant and recessive model. Haplotype analysis was performed by means of the Haploview software. Positive (PPV) and negative (NPV) predictive values were calculated for identified genetic markers. Overall, 249 patients were included. No statistically significant results for any of the included SNPs were found at analysis of the overall population. Stratified analysis demonstrated that minor homozygous genotypes of VEGF-A -2578 C>A and -460 T>C (AA and CC, respectively) conferred protection against recurrent structural disease in AJCC/UICC stage I-II and ATA low-intermediate risk patients (p=0.035 with RR 0.17 and p=0.031 with RR 0.16, respectively). Haplotype analysis of VEGF-A SNPs identified 3 common haplotypes: the -2578C, -460T, +405C (CTC); the -2578A, -460C, +405G (ACG); the -2578C, -460T, +405G (CTG). ACG and CTG haplotypes were associated with the rate of structural recurrent disease in AJCC/UICC stage I-II (p=0.05 with OR 0.22 and 0.005 with OR 2.6, respectively) and ATA low-intermediate risk patients (p=0.036 with OR 0.51 and 0.039 with OR 1.93, respectively), exerting protective and deleterious effect, respectively. Analysis of combined-SNPs genotype found that the ACG homozygous genotype (ACG+/+) offered a protective effect against structural recurrence in both stage I-II (p=0.018, RR 0.2) and ATA low-intermediate (p=0.035, RR 0.17) risk patients, whereas the CTG homozygous genotype (CTG+/+) was significantly associated to higher rate of structural recurrence in stage I-II (p=0.018, RR=3.55), and was slightly deleterious also in ATA low-intermediate risk (p=0.079, RR=2.59) subjects. The ACG+/+ genotype retained its prognostic effect in ATA low-intermediate risk patients after adjustment for tumour size and multifocality. Both ACG+/+ and CTG+/+ genotypes showed high NPV, but only CTG+/+ revealed acceptable PPV for structural recurrent disease (42.8% and 33.3% in stage I-II and ATA low-intermediate risk patients, respectively). Analysis of germline VEGF-A SNPs may refine risk stratification of DTC with “early” disease by providing stable and easily accessible prognostic markers. The validation of these markers may facilitate clinical decision-making, which is still challenging regarding several therapeutic aspects. The relevance of VEGF-A genetic variability in this group of DTC may provide rationale for considering VEGF-A targeted therapies as a possible tool for the treatment of subjects harbouring the disease recurrence risk genotype.