How common is PIK3CA mutation in breast cancer?
Different types of breast cancer can be classified from the status of
hormone receptor, i.e. estrogen receptor (ER) and progesterone receptor
(PR), and human epidermal growth factor receptor 2 (HER2). There are 60%
of breast cancer patients in the HR+/HER2- (hormone receptor-positive
and human epidermal growth factor receptor-negative) group. In HR+/HER2-
metastatic breast cancer, approximately 40% of the patients carry PIK3CA
How does PIK3CA mutation affect breast cancer treatments?
The purpose of performing PIK3CA genetic testing is to determine
personalized breast cancer treatment plans for patients. Unlike germline
mutation (for example, BRCA1 and BRCA2 heritable mutations), PIK3CA
somatic mutation will not inherit to the next generation. Patients with
PIK3CA somatic mutation are more likely to develop brain metastases2 and
present a worse overall survival (OS)3. Also, they perform poorly in
hormone therapy and chemotherapy.4 This increased the difficulty in
treating breast cancer with PIK3CA mutation.
Therefore, performing PIK3CA genetic testing, especially on HR+/HER2-
breast cancer patients, can help personalise treatment options, such as
Piqray (alpelisib), a targeted therapy targeting PI3K signalling.