Is breast cancer hereditary? Are sisters and daughters of breast cancer patients at greater risk of developing cancer? How to prevent and treat it early? These questions are frequently asked by many people in clinical practice. At yesterday’s Breast Cancer Care event organized by Susan G. Komen and United Family Healthcare China, Professor Leng Jiahua of Peking University Cancer Hospital gave a detailed explanation. Most breast cancers are clinically acquired and about 10% of breast cancers in China are familial. Familial breast cancer refers to the clustering of breast cancer in the family, i.e. at least two or more first- and second-degree relatives in the family have primary breast and/or ovarian cancer, or bilateral breast cancer patients. The BRCA1/2 genes are the two susceptibility genes most closely associated with the development of familial breast cancer. Foreign studies have shown that women carrying mutations in BRCA1 and BRCA2 genes have 10 times higher risk of breast cancer than the normal population, and their cumulative lifetime risk of developing breast cancer is as high as 60%-80%. Currently, BRCA1/2 gene testing is routinely performed for familial breast cancer patients and healthy female members of their families in Europe and the United States. Breast Cancer Genetic Factors ≠ Hereditary Breast Cancer ≠ Familial Breast Cancer If a patient is highly suspected of having hereditary breast cancer or is clearly hereditary, the biggest problem is that healthy members of the family who are related to the patient may also carry the disease-causing gene mutation, and women carrying these gene mutations will have a much higher lifetime risk of developing breast cancer. It is recommended that those at high risk who meet the conditions of family genetic predisposition should be tested for breast cancer susceptibility mutations. The age of screening for healthy women who are highly suspected or definitively carry the mutations needs to be advanced by at least 10 years. Screening using diagnostic breast imaging is generally recommended starting around the age of 25-30. What is breast cancer susceptibility gene mutation testing? Leng Jiahua introduced the BRCA1/2 germline mutation detection platform of the Breast Center Laboratory of Peking University Cancer Hospital, which mainly provides the standard BRCA1/2 gene full coding sequence detection for the examinees. In the data provided by this laboratory, analysis of 6,200 breast cancer BRCA1/2 germline mutation tests revealed that the BRCA1/2 mutation rate in familial breast cancers younger than 40 years old was as high as 28.9%, and 50% of the mutations were Chinese population-specific mutations. A proportion of familial breast cancers are due to pathogenic germline mutations in susceptibility genes. According to the data given by Prof. Leng Jiahua, BRCA1/2 is the most important susceptibility gene for breast cancer, and the germline mutation rate in familial breast cancer in Europe and the United States is 15%-20%, and the cause of nearly 80%-85% of familial breast cancer is not clear. The lifetime risk of breast cancer in European and American populations carrying BRCA1/2 mutations is 65%-85% for BRCA1 and 45%-85% for BRCA2, respectively. Therefore, without detecting the BRCA1/2 mutation, people at risk need to undergo regular breast examination. The frequency of BRCA1 mutation in triple negative patients at the age of 50 is 10.5%, and it is recommended that triple negative patients less than or equal to 50 years old should be included in the suitable population for BRCA1 gene testing. The recommendation is to perform total mastectomy on the affected breast or even on both sides.