ESR1 PvuII polymorphism: from risk factor to prognostic and predictive factor of the success of primary systemic therapy in advanced breast cancer.

BACKGROUND: The ESR1 gene encodes Estrogen Receptor alpha (ERα), which plays a role in the tumourigenesis of breast cancer. A single nucleotide polymorphism (SNP) in intron 1 of this gene called ESR1 PvuII (rs2234693) has been reported to increase the risk of breast cancer. This study aimed to investigate the ESR1 PvuII polymorphism as a prognostic and predictive factor guiding the choice of therapy for advanced breast cancer. METHODS: This retrospective study was conducted in 104 advanced breast cancer patients at Dharmais Cancer Hospital from 2011 to 2018. The ESR1 PvuII polymorphism was analysed by Sanger sequencing of DNA from primary breast tumour samples. RESULTS: The percentages of patients with ESR1 PvuII genotypes TT, TC, and CC were 42.3, 39.4, and 18.3%, respectively. Looking at prognosis, patients with ESR1 PvuII TC + CC had shorter overall survival than those with the TT genotype [HR = 1.79; 95% CI 1.05-3.04; p = 0.032]. As a predictive marker, TC + CC was associated with shorter survival (p = 0.041), but TC + CC patients on primary hormonal therapy had a median overall survival longer than TC + CC patients on primary chemotherapy (1072 vs 599 days). CONCLUSION: The ESR1 PvuII TC + CC genotypes confer poor prognosis in advanced breast cancer, but these genotypes could be regarded as a good predictor of the therapeutic effect of hormonal treatment.