Breast cancer is the most common cancer among Thai women and continues to increase each year. With advances in medical technology, breast cancer can now be diagnosed at an early stage. Genetic testing can also detect abnormalities in germ-line mutations — the genes inherited from one’s parents — to assess cancer risk and help prevent its development. The most commonly associated genetic abnormalities with breast cancer are mutations in the BRCA genes.

What is the BRCA gene?

The BRCA genes include BRCA1 and BRCA2, found in both women and men. They help repair damaged DNA and prevent abnormal cell growth. Women with mutations in BRCA1 or BRCA2 have a higher risk of breast and ovarian cancers. The lifetime risk of breast cancer in the general female population is about 12%, but women with a BRCA mutation have an increased lifetime risk of up to about 60%. In addition, women with these mutations have an increased lifetime risk of ovarian cancer from 1.4% to 15–45%.

 

People with abnormal BRCA genes also have higher risks of cancers such as cervical, endometrial, testicular, prostate, pancreatic, and other gastrointestinal cancers.

 

Who should be screened for BRCA1 and BRCA2 mutations?

1. Individuals diagnosed with breast cancer at age ≤45 years.
2. Individuals diagnosed with breast cancer at ages 46–50 years plus any of the following:
2.1 A history of more than one primary breast cancer, either at the same time or at different times.
2.2 At least one first-degree relative with breast, ovarian, pancreatic, or prostate cancer.
3. Individuals diagnosed with breast cancer at age ≥50 years plus any of the following:
3.1 At least one first-degree relative with breast cancer diagnosed at age ≤50, male breast cancer, ovarian cancer, pancreatic cancer, or prostate cancer.
3.2 At least three family members with breast cancer.
3.3 At least two first-degree relatives with breast or prostate cancer.
4. Individuals with breast cancer at any age who meet either of the following:
4.1 Triple-negative breast cancer.
4.2 Male breast cancer.
5. A first-degree relative (father, mother, sibling, or child) with breast cancer who has a confirmed BRCA1 or BRCA2 mutation.

 

For people without a cancer diagnosis, a positive BRCA1 or BRCA2 result indicates increased cancer risk but does not mean cancer is inevitable. A negative result does not eliminate cancer risk; it means the risk is similar to that of the general population.

 

For patients with breast or ovarian cancer who are found to have a BRCA mutation, the result can help physicians tailor targeted treatments.