Cancer risk and BRCA genes – the future can sometimes be known
At OncoCare Cancer Centre, Singapore, we see many patients with their families who come to provide support for the patient and often are involved in the discussion of care for the patient. Frequently, a relative may ask (or just think in their mind) what the implication of the relatives’ cancer on their own chance of cancer.
This is often a tricky question to answer because of the dynamics of the relationship between the person asking and the patient. Often, the relative probably wants an answer that everything is actually okay and that this cancer is really nothing to do with them. The fact is that being a close relative, there is an elevated risk compared to a person without a close relative of the particular cancer. This fairly general statement means that being a close relative; one would have shared environmental exposures and may have some genetic traits in common. There is close environmental and genetic interaction in cancer development. However, in some uncommon families, the genetic mutation that they carry increases their risk many times. These inherited mutations play a major role in the development of about 5% to 10% of all cancers.
Family history can sometimes give a clue to the presence of hereditary cancer
Preventive surgery for breast cancer for some BRCA1 or BRCA2 mutation carriers
Well-read patients and relatives may ask about Ms Angelina Jolie and her decision to come out in the open regarding her choice of preventive or prophylactic double mastectomy, removing her breasts before any cancer occurs. She has also recently announced that she is removing her ovaries to prevent cancer. Ms Jolie carries a “faulty” copy of the BRCA1 gene and her mother had died of ovarian cancer. A mutation carrier of this uncommon BRCA1 gene has up to an 80% chance of getting breast cancer, compared to about 6% for a woman in Singapore. Ovarian cancer risk is also increased in these women. Although there are some ranges for the risks for cancer associated with carrying a mutated gene in BRCA1 or BRCA2, it is consistently high across studies conducted in Singapore and also many other countries. In addition, other cancers are also seen in higher frequencies in such families such as prostate cancer, male breast cancer, fallopian tube cancer, primary peritoneal carcinoma and pancreatic cancer. Individuals with BRCA2 mutations may also be at increased risk for melanoma (a type of skin cancer). In addition, the breast cancer that develops is often hormone and Her2 negative, referred to as triple negative breast cancer (TNBC).
One of my favourite movies, X-Men: Days of Future Past, shows the heroes trying to prevent future disasters by time travel, having knowledge of what might happen next. Does it apply when we are able to find out a future cancer risk for an individual?
Our own study and follow up of Singapore families (Cancer Epidemiology, Biomarkers and Prevention 2007) with BRCA1 or BRCA2 mutation have diagnosed several close family kindred who developed breast or ovarian cancer later on. Some of the family members have made a decision for preventive surgery while others have chosen to continue screening. Even then, an in-depth discussion about the possible alternatives and prevention options is important and needed.
Dr Peter Ang
MMed (Int Med)
FAMS (Medical Oncology)