Table 8. Clinical Practice Guidelines for Diagnosis and Colon Surveillance of Familial Adenomatous Polyposis (FAP) continued...
In addition, endometrial cancer has been reported to be more common in MSH6 families. In the same study, the cumulative risk of uterine cancer was significantly higher in MSH6 mutation carriers (71%) than in MLH1 (27%) and MSH2 (40%) mutation carriers (P = .02). The mean age at diagnosis of endometrial carcinoma was 54 years in MSH6 mutation carriers (n = 29; range, 43–65 years) versus 48 years and 49 years in MLH1 and MSH2 mutation carriers, respectively. A group of researchers reported on ten MSH6 kindreds with LS in which 70% of females had been diagnosed with endometrial cancer compared with 31% and 29% in MLH1 and MSH2 carriers, respectively. One study found the prevalence of endometrial carcinoma to be 58% in 12 MSH6 families with a mean age at diagnosis of 57 years.
One group of researchers assembled the largest series of MSH6 mutation carrier families to estimate penetrance of cancers. A total of 113 families of MSH6 mutation carriers from five countries were ascertained through family cancer clinics and population-based cancer registries. The families contained an estimated 1,043 mutation carriers. By age 70 years, 22% (95% CI, 14%–32%) of male MSH6 mutation carriers developed CRC compared with 10% (95% CI, 5%–17%) of female MSH6 mutation carriers. By age 80 years, 44% (95% CI, 28%–62%) of male MSH6 mutation carriers were diagnosed with CRC, compared with 20% (95% CI, 11%–35%) of female MSH6 mutation carriers. For all MSH6 mutation carriers, the increased risk of CRC, relative to that of the general population, across all age groups was statistically significantly elevated (HR, 7.6; 95% CI, 5.4–10.8; P < .001). By ages 70 years and 80 years, 26% (95% CI, 18%–36%) and 44% (95% CI, 30%–58%), respectively, of women would be diagnosed with endometrial cancer. Female MSH6 mutation carriers had an endometrial cancer risk that was about 25 times higher than women in the general population (HR, 25.5; 95% CI, 16.8–38.7; P < .001).
In the same study, female MSH6 mutation carriers had a cumulative risk of other Lynch cancers (i.e., ovarian, stomach, small intestine, kidney, ureter, or brain) of 11% (95% CI, 6%–19%) by age 70 years and 22% (95% CI, 12%–38%) by age 80 years. The risk of LS cancers, excluding colorectal and endometrial cancers, was six times that of the general population (HR, 6.0; 95% CI, 3.4–10.7; P < .001). Male MSH6 mutation carriers showed no evidence of an increased risk of these cancers (HR, 0.8; 95% CI, 0.1–8.8; P = .9). The authors estimated that 24% (95% CI, 16%–37%) of men and 40% (95% CI, 32%–52%) of women harboring deleterious MSH6 mutations would be diagnosed with any LS cancer by age 70 years and that these values will increase to 47% (95% CI, 2%– 66%) of men and 65% (95% CI, 53%–78%) of women by age 80 years.