People with Lynch syndrome have a genetic mutation that gives them a high risk of several types of cancer including bowel cancer. The genes that are damaged can't repair any errors that occur in our DNA.
The study, which has been published in the Journal of Clinical Oncology, confirmed the increased risk of cancers already known to be associated with Lynch syndrome, including colon, uterus, ovary, kidney, stomach, and bladder cancers. They also found those with Lynch syndrome faced a moderately increased risk of developing breast and pancreatic cancer.
The researchers, led by Dr Aung Ko Win, and Associate Professor Mark Jenkins, at The University of Melbourne's School of Population Health, followed 450 people with a mutation in one of the four mismatch repair genes associated with Lynch syndrome, and more than 1000 of their relatives who were not carriers of these mutations. Study participants were evaluated every five years at recruitment centres affiliated with the Colon Cancer Family Registry in Australia, New Zealand, Canada and the US.
After five years, those with Lynch syndrome had a 20-fold greater risk of colorectal cancer; a 30-fold greater risk of endometrial (uterine) cancer; a 19-fold higher risk of ovarian cancer; an 11-fold greater risk of kidney cancer; a 10-fold greater risk of pancreatic, stomach, and bladder cancers; and a four-fold greater risk of breast cancer. People with Lynch syndrome also tended to be diagnosed with these cancers at an earlier age than people in the general population.
The researchers said their findings regarding breast cancer were unexpected. They said further studies were needed to determine if ages at mammographic screening or methods such as use of MRI should be recommended for people with Lynch syndrome. Currently, individuals with Lynch syndrome typically undergo colonoscopy at an earlier age than the general population, but no other special screening regimens have been agreed upon.
This is also the largest study to date of cancer risk for non-carriers of family specific mutations.
"Our study revealed that these people have an average risk of developing cancer as opposed to the high risk of their mutation-carrying close relatives and hence do not need to worry unnecessarily and over screen to detect cancer," said Associate Professor Jenkins.
"While not a common condition, approximately 20,000 Australians have Lynch syndrome and a very high risk of cancer. Over time, as improved screening methods become available, the findings may help doctors refine screening guidelines for breast, uterus, colon and other cancers among patients with Lynch syndrome. In the meantime, genetic testing will give people a clearer indication of their real risk level and clarify what they could or should not do to reduce their risks of cancer."
People who think they might be at increased risk for cancer due to family history should attend a Family Cancer Clinics for genetic testing and advice so cancers can be detected and treated as early as possible.
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