Prevalence and clinical implications of PIK3CA aberrations across cancer types: A real-world next-generation sequencing approach

Background: Activation of the phosphatidylinositol 3-kinase (PI3K) pathway is a common oncogenic mechanism in various solid tumors and is often driven by aberrations in the PIK3CA gene. Recent advancements have shown effective treatment for patients with PIK3CA-mutated breast cancer; however, there is an unmet need for other malignancies. The aim of this study was to gain a better understanding of PIK3CA mutations and amplifications across cancer types. Methods: From October 2019 to June 2023, we performed next-generation sequencing using Trusight Oncology 500 on 3886 patients with 36 different cancer types at the Samsung Medical Center. The incidence of PIK3CA mutations and amplifications according to cancer type and their correlation with the tumor mutation burden (TMB), microsatellite instability (MSI), and homologous recombination deficiency (HRD) status were reviewed. Mutation sites were also identified. Results: Among the 3886 patients, PIK3CA mutations were present in 9.2 % (358/3886) of the cohort, with colorectal cancer, 52.8 % (189/358), having the highest incidence. Patients harboring PIK3CA mutations demonstrated significantly higher TMB and MSI-high rates than those without (31.8 % vs. 12.5 % for TMB and 7.8 % vs. 1.6 % for MSI-high, respectively, p = 0.001). In contrast, PIK3CA amplifications were observed in 1.3 % (51/3886) of patients, primarily in gastric, bladder, and colorectal cancers, and associated with lower TMB, MSI-high, and HRD rates. PIK3CA fusions were identified in three patients. The most common mutation sites were E545K, E542K, and H1047R. Conclusion: Of 3886 patients with metastatic solid tumors, 358(9.2 %) had PIK3CA mutations and 51(1.3 %) had PIK3CA amplifications. Next-generation sequencing analysis provided a deeper understanding of PIK3CA aberrations.