PIK3CA mutations and PTEN loss: Effects on neoadjuvant trastuzumab in Vietnamese breast cancer patients
Abstract
The objective of this study was to ascertain the prevalence of PIK3CA mutations and PTEN loss in HER2-positive stage II–III Vietnamese breast cancer patients and evaluate their impact on the disease. This case-control study, conducted from January 2019 to June 2022, included 92 patients initially diagnosed with stage II or III breast cancer, confirmed HER2-positive, and treated with neoadjuvant trastuzumab. Post-mastectomy, patients were grouped into pathological complete response (pCR) and pathological partial response (pPR). Each patient was tested for PIK3CA mutations and PTEN loss to examine their correlation with neoadjuvant chemotherapy response. Ninety-two patients completed neoadjuvant chemotherapy and surgery. Among them, 44 (47.8%) achieved complete tumor response, 9 (9.8%) had ductal carcinoma in situ, and 39 (42.4%) had invasive breast cancer. The prevalence of PIK3CA mutations was 16.3%, primarily c.3140A>G (p.H1047R) at exon 20. The rate of PTEN loss was 26.1%. There was no observed correlation between PIK3CA mutation or PTEN loss and neoadjuvant chemotherapy response, with odd ratios of 1.22 (95% CI: 0.93–1.61) and 0.80 (95% CI: 0.63–1.01), respectively. The study revealed no evident correlation between PIK3CA mutations or PTEN loss and the pathological complete response to neoadjuvant chemotherapy. As a result, our findings recommend prudence in the consideration of PIK3CA mutations and PTEN loss as prognostic markers for neoadjuvant chemotherapy response in patients with HER2-positive stage II–III breast cancer.
Keywords: PIK3CA, PTEN, HER2, Breast cancer, Neoadjuvant chemotherapy
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