BRCA TESTING: WITH GREAT POWER COMES GREAT RESPONSIBILITY

By Dr. Nick Walker 2 years ago
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Statistics show that 1 in 35 South African women will develop breast cancer in their lifetimes. BRCA1 and BRCA2 mutations account for about 5 to 10 percent of all breast cancers and as much as 25 percent of inherited breast cancers (1, 2). These mutations also account for nearly 15 percent of all ovarian cancers worldwide (3). But what are BRCA1 and BRCA2 and how can mutations in these genes contribute to the likelihood of developing breast and ovarian cancers?

BRCA1 and BRCA2 are genes that produce proteins responsible for supressing cancers (4). These proteins help repair damaged DNA and prevent the build-up of harmful mutations that may cause cancers. When BRCA 1 and BRCA2 contain mutations, the protein coded by these genes is not effective at repairing DNA and DNA mutations begin to accumulate. This puts the cells at higher risk of becoming malignant and increases the risk of developing cancers.

Gene sequencing tools now exist to screen these genes for mutations, but who do we screen? BRCA1 and BRCA2 gene mutations are relatively rare and thus largescale, general population screening efforts are not viable. Instead, screening should only be considered when the person’s individual or family history suggests a high risk for carrying BRCA1 or BRCA2 mutations. It is also important to bear in mind that genetic counselling is usually recommended before and after any genetic screening test for an inherited disease. In the case of BRCA testing, this counselling should be performed by a health care professional who is experienced in cancer genetics. The reason for this is to ensure that the correct interpretation of the test result is effectively communicated to the patient. This is especially important if a positive test result for a mutation is discovered. The HCP needs to elaborate that a positive test result indicates that a person has inherited an increased risk of developing certain cancers and not that they necessarily will. In fact, many women are shown to have harmful BRCA mutations and without any preventative measures, never develop breast and ovarian cancers.

Similarly, a negative result does not mean that the individual will never develop breast and ovarian cancers. As mentioned earlier, BRCA mutations account for only 5-10% of all breast cancers and nearly 15% of ovarian cancers worldwide. This outlines the fact that these cancers can have many root causes, both environmental and genetic causes that are distinct from the BRCA gene group.

In the case of a positive result, it is vitally important for the physician and patient to understand the associated risk profile that having a mutation can have, as well as their options. In general, woman who have detectable mutations in BRCA1 and BRCA2 have a lifetime risk of developing breast cancer of 40 to 85%, and they have a 25 to 65% chance of developing ovarian cancer (5). However, several options are available for managing their cancer risk. These include enhanced screening, prophylactic surgery, and chemoprevention.

In summary, BRCA screening can be extremely useful to health care professionals and patients alike. However, it is vital that the results of the testing are properly understood by the healthcare professional and more importantly, the patient. Risk mitigation options vary in intensity from minimal (enhanced screening) to drastic (prophylactic surgery, and life-long chemoprevention).  For this reason, it is vital that the correct options are discussed and responsible decisions made with reference to the individuals risk factor.

References:

  1. Easton DF. How many more breast cancer predisposition genes are there? Breast Cancer Research 1999; 1(1):14–17.
  2. Campeau PM, Foulkes WD, Tischkowitz MD. Hereditary breast cancer: New genetic developments, new therapeutic avenues. Human Genetics 2008; 124(1):31–42.
  3. Pal T, Permuth-Wey J, Betts JA, et al. BRCA1 and BRCA2 mutations account for a large proportion of ovarian carcinoma cases. Cancer 2005; 104(12):2807–16.
  4. https://www.cancer.gov/about-cancer/causes-prevention/genetics/brca-fact-sheet
  5. by S Pruthi.‎ Identification and Management of Women With BRCA Mutations or Hereditary Predisposition for Breast and Ovarian Cancer. Mayo Clin Proc. 2010 Dec; 85(12): 1111–1120.
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 Dr. Nick Walker

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