Knowledge becomes power when you know your genetic background
They are some of the most dreadful words a woman will ever hear: “Your test for breast cancer is positive.”
The good news is that increasingly sophisticated genetic tests are being developed throughout the world, almost daily, to determine the possibility of someone developing the disease in the future. Some tests, after diagnosis, can help a medical team decide on treatment tailored specifically for individuals.
Awareness puts you on your guard. It could even, with the correct prophylactic measures, significantly reduce your risk of contracting breast cancer. It certainly means you won’t land up in the position my poor sister did. Anne was diagnosed overnight in November 2000 with 4th-stage breast cancer that had spread throughout her body and she was given two weeks to live. She died in June the next year.
New diagnostic measures could mean no mastectomy. They might prevent chemotherapy.
One test can measure the potential of a woman’s cancer spreading to other parts of the body. “It could save 20%-30% of women from having chemotherapy — the most dreaded part of cancer,” says Dr Maritha Kotze, a geneticist at the University of Stellenbosch’s pathology department.
She has organised workshops in Pretoria and Cape Town to explain the latest developments in genome research as part of breast cancer awareness month, in October. She calls it GeneTalk and the focus is on genetic testing to help doctors decide how to treat a particular patient. “You can’t just test someone for everything. We need to fit a genetic test into a person’s risk profile and family history.”
All breast cancers are caused by genetic abnormalities or mutations, which are either inherited or nonhereditary (acquired). An inherited genetic abnormality can be passed from a parent to a child — male or female. They have a 50% chance of inheriting the faulty gene. A nonhereditary genetic abnormality is caused by an error during gene production or from environmental factors like hormonal influences, toxic exposure or a bad diet (eating too much junk food).
There are two major genes for inherited breast cancer — BRCA1 and BRCA2. DNA testing for these is frequently considered for the following reasons:
- To screen at-risk family members for a mutation (abnormality) already known because somebody close to you — a mother or sister — has been diagnosed with breast cancer.
- To screen for a limited number of mutations known to cause cancer in certain groups (Ashkenazi Jews or Afrikaner Caucasians).
“It’s important to remember that despite the increased risk, not everybody with an inherited BRCA1/2 abnormality will develop cancer,” says Kotze. “Women without an inherited breast-cancer gene abnormality have about a 10% risk of developing breast cancer over a 90-year life span.”
She recommends the test if you have a family history of early breast cancer. You are at risk if you have:
- Four close relatives diagnosed under the age of 60.
- Three close relatives diagnosed under the age of 50.
- Two close relatives under 60 plus ovarian cancer in your family.
- Male breast cancer and any family history of breast cancer.
Women who are anxious about their cancer risk or family history can benefit from genetic counselling. Kotze offers this counselling through a company, Gknowmix, which she has established with other academics.
During the session you, and perhaps close relatives, can decide whether it’s a good idea to have the DNA test, based both on your particular situation and a risk assessment after a detailed family pedigree is drawn up. Tests are not done on girls under 18. If you decide to have the test and it proves positive, it doesn’t mean you will definitely get breast cancer, though many women with an abnormal gene assume they will, says Kotze. “This can trigger anxiety, anger or depression, which is why it’s so important to have both pre- and post-test genetic counselling.” This can be done by registered genetic counsellors or medical doctors who are knowledgeable in the field of genetics.
Prof Justus Apffelstaedt is associate professor of surgery at the University of Stellenbosch and is head of the Breast Clinic at Tygerberg Hospital. He says healthy person who has an abnormal test result or has a mother or sisters with pre-menopausal breast cancer, should have “tightened surveillance by breast ultrasound and mammography before the usual recommended screening at the age of 40”. This is to ensure any signs of cancer are picked up early, when cancer is most treatable and curable, he says.
Some women may consider a prophylactic mastectomy before cancer cells can even form. However, while this reduces the risk significantly, it does not eliminate it entirely, says Kotze. Clearly knowledge becomes power when you know your genetic background and risk. A landmark study of Ashkenazi Jewish women with breast cancer by the New York Breast Cancer Study Group, published in Science in 2003, showed a healthy lifestyle could protect women with BRCA1/2 mutation carriers from developing cancer. The research revealed that women who exercised and ate sensibly to avoid becoming obese were able to delay significantly the onset of breast cancer.
Another breast-cancer test has become available in SA recently. Called a MammaPrint test, it’s usually performed on a tumour biopsy removed when the patient is having breast surgery. It’s done to assess the risk of cancer spreading to other parts of the body. If it’s done in the early stages of cancer, it can predict the risk of metastases with greater accuracy than is possible at present using conventional methods, says Kotze.
There is about a 25% reduction of breast-cancer patients being classified as high risk when the genetic test is used. “About 60% are classified high risk compared with 85% based on clinical features only,” says Apffelstaedt. Clinical features include the size of a tumour and number of lymph nodes.
Patients with a poor prognosis profile have a one in two chance of developing metastases and dying within 10 years, he says. “They need aggressive chemotherapy to improve their chances of survival, even in the case of small tumours and no lymph node infiltration.”
Women with a good prognosis profile have only a 4% chance of developing metastases and dying and therefore don’t need aggressive and unpleasant treatment. “Many doctors may feel they can’t advise a patient to have a genetic test before treating them, because they want to act immediately and it can take a week or more before we get results,” says Kotze.
Published with permission: Published in the Business Day, Oct 2008.