CHICAGO – Lynch syndrome can predispose individuals to a number of different cancer types, including colorectal tumors, but the results of a preliminary study found that the incidence may be lower than what has been previously reported.
New findings presented at Digestive Disease Week® showed that the incidence of colorectal cancer after screening with colonoscopy ranged from 6.3% to 25.9%, depending on the specific mutated gene. This is in contrast to other reports which have found a 50% increase in the incidence of colorectal cancer in individuals with Lynch syndrome.
“We looked at the incidence of colorectal cancer and other associated cancers in individuals with Lynch syndrome and how screening can have an impact on that,” said study author Ariadna Sanchez, MD, from the Hospital Clínic de Barcelona, Spain.
She emphasized that the results being presented at the meeting are preliminary and, thus, will need further confirmation, but it is a multicenter study and is being conducted in more than 1,100 patients.
“The diagnosis of colorectal cancer with screening colonoscopy is lower than results that have been previously published,” she said. “This finding reinforces the importance of screening colonoscopies in patients with Lynch syndrome.”
As to why their rates are lower, Dr. Sanchez speculated that it may be because precancerous polyps are being removed with screening.
“Our thinking is that, as we perform screening and remove the polyps, then in theory, cancer will be prevented,” she explained, “since they didn’t have the opportunity to continue to progress into cancer.”
In other words, screening this high-risk population may not only identify those who have cancer but may prevent it from developing in others.
Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), is an inherited disorder that increases the risk of many types of cancer, including colorectal and cancers of the stomach, small intestine, liver, gallbladder ducts, upper urinary tract, brain, skin, ovaries, and endometrium.
Caused by germline mutations in the mismatch DNA repair system (MLH1, MSH2, MSH6, PMS2), it has been difficult to make precise estimates of cancer risk in individuals with the syndrome because of retrospective studies and small cohorts.
Dr. Sanchez and her colleagues conducted a multicenter nation-wide study in Spain with the goal of establishing the cumulative incidence of colorectal cancer and other tumor types in Lynch syndrome and to evaluate the effect of screening surveillance on cancer incidence. Cancer-specific survival will also be assessed.
The cohort included 1,108 patients with Lynch syndrome from 25 centers, who were followed-up for a mean of 67.5 (± 57.8 months).
The first colonoscopy screening detected cancer in 49 patients (MLH1, n = 23/268; MSH2, n = 18/249; MSH6, n = 4/154; PMS2, n = 2/47; EPCAM, n = 2/13), extrapolating to a cumulative incidence of 25.6% for MLH1, 22.1% for MSH2, 6.3% for MSH6, and 25.9% for PMS2 mutation carriers.
Most patients were diagnosed with stage 1 disease (45.7%) and, to a lesser degree, with stage II (28.6%), stage III (22.9%), and stage IV (2.9%).
The 10-year cumulative incidences for subsequent colorectal cancers for patients who had a previous diagnosis of the disease were 9.4% (95% CI, 5-17) for MLH1, 12.6% (95% CI, 5.6-27.6) for MSH2, and 17.2% (95% CI, 6.6-40) for MSH6.
Digestive Disease Week is jointly sponsored by the American Association for the Study of Liver Diseases (AASLD), the American Gastroenterological Association (AGA) Institute, the American Society for Gastrointestinal Endoscopy (ASGE), and the Society for Surgery of the Alimentary Tract (SSAT).