Date：2021-12-14

What is PIK3CA mutation?

PIK3CA gene is responsible for encoding the p110α protein. The function of this protein includes the control of cell growth and division. When the PIK3CA gene mutates, it leads to uncontrolled growth and spread of cells and cancer development. PIK3CA mutations can be found in some cancer types, including breast cancer.

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 mutation.¹

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.

Source:

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2. Fitzgerald, D & Muzikansky, A & Pinto, C & Henderson, L & Walmsley, C & Allen, R & Ferraro, G & Isakoff, Steven & Moy, B & Oh, K & Shih, H & Dias-Santagata, Dora & Iafrate, A & Bardia, A & Brastianos, P & Juric, Dejan. (2019). 318PAssociation between PIK3CA mutation status and development of brain metastases in HR+/HER2- metastatic breast cancer. Annals of Oncology. 30. 10.1093/annonc/mdz242.013
3. Mosele F, Stefanovska B, Lusque A, Tran Dien A, Garberis I, Droin N, Le Tourneau C, Sablin MP, Lacroix L, Enrico D, Miran I, Jovelet C, Bièche I, Soria JC, Bertucci F, Bonnefoi H, Campone M, Dalenc F, Bachelot T, Jacquet A, Jimenez M, André F. Outcome and molecular landscape of patients with PIK3CA-mutated metastatic breast cancer. Ann Oncol. 2020 Mar;31(3):377-386. doi: 10.1016/j.annonc.2019.11.006. Epub 2020 Jan 24. PMID: 32067679.
4. Brown KK, Toker A. The phosphoinositide 3-kinase pathway and therapy resistance in cancer. F1000prime Reports. 2015 ;7:13. DOI: 10.12703/p7-13. PMID: 25750731; PMCID: PMC4335789.