Penetrance of colorectal cancer among MLH1/MSH2 carriers participating in the colorectal cancer familial registry in Ontario

<p>Abstract</p> <p>Background</p> <p>Several DNA mismatch repair (MMR) genes, responsible for the majority of Lynch Syndrome cancers, have been identified, predominantly <it>MLH1 </it>and <it>MSH2</it>, but the risk associated with these mutations is still not well established. The aim of this study is to provide population-based estimates of the risks of colorectal cancer (CRC) by gender and mutation type from the Ontario population.</p> <p>Methods</p> <p>We analyzed 32 families segregating MMR mutations selected from the Ontario Familial Colorectal Cancer Registry and including 199 first-degree and 421 second-degree relatives. The cumulative risks were estimated using a modified segregation-based approach, which allows correction for the ascertainment of the Lynch Syndrome families and permits account to be taken for missing genotype information.</p> <p>Results</p> <p>The risks of developing CRC by age 70 were 60% and 47% among men and women carriers of any MMR mutation, respectively. Among <it>MLH1 </it>mutation carriers, males had significantly higher risks than females at all ages (67% vs. 35% by age 70, p-value = 0.02), while the risks were similar in <it>MSH2 </it>carriers (about 54%). The relative risk associated with <it>MLH1 </it>was almost constant with age (hazard ratio (HR) varied between 5.5-5.1 over age 30–70), while the HR for <it>MSH2 </it>decreased with age (from 13.1 at age 30 to 5.4 at age 70).</p> <p>Conclusion</p> <p>This study provides a unique population-based study of CRC risks among <it>MSH2</it>/<it>MLH1 </it>mutation carriers in a Canadian population and can help to better define and understand the patterns of risks among members of Lynch Syndrome families.</p