October 24, 2017
New research which has dramatically expanded the number of known risk factors for breast cancer is set to pave the way for earlier screening and better drugs for those in the disease’s firing line.
The world’s biggest genetic study of the illness has uncovered 72 new variants that put women at higher danger and could allow screening for women with family histories of breast cancer in their 20s or 30s. Revealed this morning in two Nature journals, the study casts new light on family risk factors for breast cancer and provides insight into how genetic variations, which pose little danger on their own, can combine to increase the risk of contracting breast cancer.
The international effort involved 550 researchers from about 300 institutions including six universities, five hospitals, a charity and two medical research institutes in Australia. Collectively they analysed data from 275,000 women, more than half of whom were diagnosed with breast cancer.
While mutations in well-studied genes like BRCA1 and BRCA2 boost the probability of contracting the disease, more than 100 less consequential variants — which pose little danger individually, but considerable risk collectively — had already been implicated. The new study raises that number to about 180, explaining a further 18 per cent of the “familial relative risk” for breast cancer.
Co-lead author Georgia Chenevix-Trench, of the QIMR Berghofer Medical Research Institute in Brisbane, said tests for the markers could highlight women who warranted early mammograms or MRIs. The insights could be particularly helpful in determining whether and when women at high risk, because of BRCA mutations, should have preventive surgery. The “genotyping” tests would measure several hundred variants, as opposed to full genome sequencing which is far more expensive. Professor Chenevix-Trench said such tests were already being used in research, and could be clinically available in a few years.
Brisbane author Josie Dietrich said such tests “would have saved me a great deal of suffering. I would have had a chance of having a second child.” Diagnosed with a “very aggressive” cancer at 35, she had a double mastectomy, a full hysterectomy and chemotherapy. Eight years later she still takes drugs that could cause osteoporosis, necessitating infusions twice a year to keep her bones strong.
The treatment and its effects are like a “chronic disease”, even though she is now clear of cancer. “I’ve gone through the menopause from hell, and I’m only 43. A geneticist said I had what’s called an unspecified inherited cluster, which means there are all these reasons I got cancer — but no one really knows why.”
Professor Chenevix-Trench said the findings could guide development of new drugs. While most of the suspect variants were found in “non-coding” parts of the genome — stretches of genetic material that do not generate proteins, long dismissed as “junk DNA” — they could help pinpoint proteins to be targeted.