Background & aims: 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.
Methods: 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.
Results: 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.
Conclusions: 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.