Abstract P5-02-52: Predictive and prognosis value of PIK3CA mutations in HER2-positive breast cancer treated with tyrosine kinase inhibitors (TKIs): a systemic review and meta-analysis

Abstract Background: PIK3CA mutations is one of the most frequent gene alterations in breast cancers, which was reported to be related to the treatment response of anti-HER2 regimens. However, the relationship between PIK3CA mutations and treatment response of a tyrosine kinase inhibitors (TKIs) is still unclear. We thus conducted a systemic review and meta-analysis to investigate the predictive and prognosis value of PIK3CA mutations in HER2-positive breast cancer treated with TKIs. Methods: The following databases were searched from inception to July 2022: Medline, Embase and the Cochrane Library. Abstracts from conferences were also reviewed for inclusion. The critical information was extracted from eligible studies. Results: A total of 16 reports including 17 studies were assessed for eligibility, enrolling 1706 patients. Ten studies including 902 patients were in the neoadjuvant setting, the pCR rate is significantly higher in PIK3CA wild-type (WT) patients than in mutated-type (MT) patients (OR = 0.45; 95% CI: 0.31-0.65; P< 0.001). Seven studies including 804 patients were in the metastatic setting, the pooled objective response rate (ORR) is significantly higher in PIK3CA WT patients than in MT patients (OR = 0.40; 95% CI: 0.23-0.70; P = 0.001), and similarly, the clinical benefit rate (CBR) in WT patients is also higher (OR = 0.43; 95% CI: 0.19-0.98; P=0.045). A total of 4 metastasis studies reported progression free survival (PFS), and 2 of them reported overall survival (OS), revealing a marginally significant relationship between PIK3CA mutation and worse PFS (HR = 0.82; 95% CI: 0.67-1.00; P=0.052) and OS (HR=0.63, 95%CI:0.39-1.02; P=0.062). No evidence of publication bias was found in both the neoadjuvant setting and metastatic setting. Conclusion: Our findings indicate that PIK3CA mutations is significantly associated with a lower rate of pCR when treated with TKI-containing regimens in neoadjuvant chemotherapy of early-stage HER2-positive breast cancer, and is significantly associated with lower ORR and CBR in metastatic HER2-positive breast cancer. Citation Format: Qiyun Shi, Juncheng Xuhong, Hao Tian, Yi Zhang, Jun Jiang, Xiaowei Qi. Predictive and prognosis value of PIK3CA mutations in HER2-positive breast cancer treated with tyrosine kinase inhibitors (TKIs): a systemic review and meta-analysis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-02-52.