Better survival rates in patients with MLH1-associated hereditary colorectal cancer

Patients with hereditary nonpolyposis colorectal can cer (HNPCC) have been suggested to have a better prognosis than patients with common sporadic colorectal cancer. However, the evidence has not been convincing. The aim of this population-based study was to compare the survival rates of 175 patients with HNPCC with those of 14,000 patients with sporadic colorectal cancer diagnosed at <65 years of age in Finland from 1953 to 1993.

The recent progress in molecular genetics of hereditary colorectal cancer was utilized for the first time. One hundred twenty of the patients with HNPCC came from families segregating a germline mutation in the MLH1 cancer predisposition gene.

The overall 5-year cumulative relative survival rate was 65% for patients with HNPCC and 44% for patients with sporadic colorectal cancer. The relative survival rates of patients with HNPCC were better in every strata analyzed.

MLH1-associated colorectal cancer has a natural history different from that of common sporadic colorectal cancer. The better survival rates may be caused by the heavy mutation burden affecting mismatch repair deficient tumor cells.