Mutation Detection of Phosphatidylinositol-4,5-bisphosphate 3-Kinase Catalytic Subunit Alpha for Treatment Guidance in Breast Cancer

Molecular analysis of breast cancer tissue has revealed that breast cancer is not a uniform disease. Each breast cancer patient has several molecular signatures that differ from those of others. Therefore, breast cancer therapy should be personalized, depending on its molecular signatures. Breast cancer with hormonal receptors can be treated with a selective estrogen receptor modulator or selective estrogen receptor degrader therapy, while breast cancer with overexpression of human epidermal growth factor receptor 2 (HER2)-neu gene responds excellently to anti-HER2-neu therapy. For patients with advanced breast cancer that already has distant metastasis and a poor prognosis, a new agent has been discovered. The phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) inhibitor has been proven effective in treating advanced breast cancer with a PIK3CA gene mutation. This therapy can be administered to HER2-negative breast cancer patients and in combination with selective estrogen receptor degrader therapy for post-menopausal patients with positive hormonal receptors. Although this treatment is effective, it cannot be given to every advanced breast cancer patient. Before administering the treatment, a PIK3CA mutation test is compulsory. PIK3CA mutation detection in breast cancer can predict the cancer's response to the PIK3CA inhibitor, providing information on which patients will benefit from the treatment.