INVESTIGATION OF EXON20 PIK3CA GENE MUTATION IN PLASMA OF HORMONE RECEPTOR POSITIVE BREAST CANCER PATIENTS

Abstract

Objective: To determine the frequency of H1047R mutation on exon 20 PIK3CA gene in the plasma of hormone recepter positive (HR+) breast cancer (BC) women and its relationship with clinical characteristics of these patients. Subjects: Plasma was separated from venous blood of 141 female HR+ BC patients, have been treating at 108 Military Central Hospital from June 2021 to June 2023. Method: Circulating free DNA (cfDNA) was isolated from plasma by magnetic beads (Thermo Fisher Scientific). The H1047R hotspot mutation on exon 20 PIK3CA gene was detected in 141 plasma samples by an in-house Realtime PCR assay using a wild-type allele-specific blocker. Results: 47/141 samples (33,3 %) had the H1047R mutation. The H1047R mutation was present in all disease stages, both in metastatic and non-metastatic cases. Although, the rates of gene mutation in late-stage, metastatic cancer patients were higher than those in the early-stage, non-metastatic cancer group, there was no statistically significant difference between the two groups (p > 0.05). Whereas it was not linked to other clinical traits of patients with HR+BC, the H1047R mutation was more common in those with liver metastases and in those received Fulvestrant (p < 0.05). Conclusion: Peripheral blood from patients with HR+BC in all stages contained the H1047R mutation on exon 20 of the PIK3CA gene. This mutation frequently developed in patients received Fulvestrant treatment and has been related to liver metastases.