A genetic defect that may increase the lifetime risk of ovarian cancer by up to 40 per cent has been identified for the first time. This breakthrough of finding the first common genetic variant uniquely linked to ovarian cancer could enable a genetic screening programme to identify those women most at risk. Findings from this research, carried out at University College London and the Cancer Research UK Genetic Epidemiology Unit at the University of Cambridge, have been published in the journal Nature Genetics.
The UK researchers searched through the genomes of 1,810 women with ovarian cancer, and 2,535 women without the disease, from across the UK. After analysing some 2.5 million genetic variations they discovered one genetic defect that was uniquely linked to risk of developing ovarian cancer. The scientists confirmed their discovery by examining data from the international Ovarian Cancer Association Consortium (OCAC) on a further 7,000 women with the disease, and 10,000 without the disease, from around the world. The defect, known as an SNP (single nucleotide polymorphism), is located on chromosome nine, and those who possess this variation on both copies of that chromosome (approximately 15 per cent of women) have a lifetime risk of ovarian cancer of 14 in 1000. The risk drops to 12 in 1000 for those who only carry one copy of the variant (about 40 per cent of women) and to 10 in 1000 for women who do not have the mutation.
Roughly five per cent of cancers diagnosed in women are ovarian, making it the fifth most common cancer, affecting roughly 6,800 UK women a year. However, it is the fourth most common cause of cancer death in UK women with 4,300 deaths from the disease each year, mostly because the cancer is extremely difficult to detect in the early stages when it is at its most curable.
'There has been little change in the prognosis for women with ovarian cancer over the last 40 years because the diagnosis is very, very late,' explained Dr Simon Gayther, a senior author of the study. 'With ovarian cancer there is a 60 per cent chance that a woman diagnosed will be dead within five years. The reason is that the ovaries lie deep in the abdomen and it often goes undiagnosed.'
Two genes, known as BRCA1 and BRCA2, were linked to a significantly increased risk of developing ovarian cancer in the late 1990s - but faults in these genes are rare and probably account for less than five per cent of cases. 'It is likely that the remaining risk is due to a combination of several unidentified genes - which individually carry a low to moderate risk. Now we have ticked one off, the hunt is on to find the rest,' stated Dr Paul Pharoah, from Cambridge University, another senior author of the study.
'There is now a genuine hope that as we find more, we can start to identify the women at greatest risk and this could help doctors to diagnose the disease earlier when treatment has a better chance of being successful,' continued Dr Gayther, adding: 'It is premature to say we are in a position to set up a screening programme at the moment, but in 10 years' time we will be in a position to identify several more of these genetic factors, then you could see screening being offered on a population level.'
