Clinicopathogenomic analysis of AKT1-PIK3CA-PTEN-altered luminal metastatic breast cancer in Japan

Abstract This rapid communication highlights the correlation between protein kinase B alpha (AKT1)-phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA)- phosphatase and tensin homolog (PTEN) alterations and clinicopathological factors in Japanese patients with metastatic recurrent breast cancer (mBC). This study analyzed 1967 patients with luminal-type breast cancer who underwent cancer gene panel testing. The results demonstrated that AKT pathway alterations, including AKT1-PIK3CA-PTEN, occurred in 1038 (52.8 %), 131 (6.7 %), and 76 (3.9 %) cases, respectively. Patients with AKT pathway mutations were older (p = 0.002) and had a higher rate of invasive lobular carcinoma (ILC) histology (p = 0.001), progesterone receptor (PgR) positivity (p = 0.006), and bone metastases (p = 0.001), and a lower rate of germline BRCA2 (p < 0.001). Comprehensive genomic profile results demonstrated a higher tumor mutational burden (TMB) (< 0.001) and lower tumor BRCA1/2 expression (< 0.001) in patients with mutations in the AKT pathway. These results are crucial for characterizing candidates for AKT pathway-targeted molecular therapies and conceptualizing optimal treatment strategies.