Heredity
In most men and women with breast cancer, the disease is caused by chance or (still) unknown factors. In approximately 5-10% of all men and women with breast cancer, it is a hereditary form. The best known ones are the BRCA1 and BRCA2 mutations. (Korde et al. 2010)
Mutation
Mutations are changes in the genetic material (DNA). These mutations can be passed on from parent to child. If a father or mother has such a mutation, their sons and daughters each have a 50% chance of inheriting this mutation from their parent.
Male-female differences in heredity
The hereditary predisposition to breast cancer can therefore be passed on to both men and women. However, breast cancer is more common in female BRCA1/2 mutation carriers than in male carriers. The risk of developing breast cancer in women is estimated at 60-80%, in men with a BRCA2 mutation this is estimated at 7%, and for a BRCA1 mutation it is below 2%. Male mutation carriers do not need regular breast examinations (as women are advised) (Korde et al. 2010)
Risk of other tumours in addition to breast cancer
Male carriers of a BRCA2 mutation have an increased risk of prostate cancer in later life. We are currently investigating what the best surveillance method is. These men can consider periodic prostate examinations from the age of 55. The pros and cons of this examination should be discussed with the doctor.
Carriers of a BRCA1 or BRCA2 gene mutation who have family members with pancreatic cancer (pancreatic carcinoma) can have the pancreas checked in a research context [see CAPS study (Canto et al. 2013)]. These checks are also still being investigated as to whether they can detect cancer in time.
Mutations other than BRCA1 and BRCA2
Other gene mutations have been identified more recently which are associated with a (moderate to strong) increased risk of breast cancer in women: CHEK2, PALB2, ATM, NF1. (Easton et al. 2015) Mutations have also been found which are very rare, but which may present a greatly increased risk of breast cancer in women: PTEN, TP53, CDH1, STK11. It’s currently not clear whether men with these gene mutations have an increased risk of breast cancer and how high that risk is. (Easton et al. 2015)
Referral for heredity testing
If a man has breast cancer, that is an indication for a referral to a clinical genetic centre. See StOET en VKGN guideline. Genetic testing can show whether someone is a carrier of a gene mutation. This knowledge can sometimes help to adjust the treatment (for example through a broader operation). In addition, the information is important to inform family members, so they can be tested for that specific mutation. Female carriers in particular can then take measures to be on time (by regularly screening with an annual mammogram or MRI), or to reduce the risk of breast cancer by undergoing a risk-reducing operation. Male carriers can monitor their breasts more consciously themselves.
Clinical Genetic Centres
A man with breast cancer, or with a suspected hereditary predisposition for breast cancer, can be referred to one of the nine outpatient clinics for familial tumours or clinical genetic centres. Clinical geneticists and genetic counsellors also often have consulting hours for hereditary breast cancer in other centres in the region. For more information about these centres: http://www.vkgn.org/voorlichting/poliklinieken-klinische-genetica/.
Patient association: Oncogen
Oncogen is part of the Dutch Breast Cancer Society (BVN). This association represents the interests of people with a hereditary or familial predisposition to breast and ovarian cancer. It also provides good information and support. The website’s emphasis is primarily on women. For more information, see: https://brca.nl/nl/oncogen.
References
Canto, M. I., et al. (2013), ‘International Cancer of the Pancreas Screening (CAPS) Consortium summit on the management of patients with an increased risk for familial pancreatic cancer’, Gut, 62 (3), 339-47.
Easton, D. F., et al. (2015), ‘Gene-panel sequencing and the prediction of breast cancer risk’, N Engl J Med, 372 (23), 2243-57.
Korde, L. A., et al. (2010), ‘Multidisciplinary meeting on male breast cancer: summary and research recommendations’, J Clin Oncol, 28 (12), 2114-22.