Purpose: Little is known about colorectal cancer in young patients at a population level, and the behavior, characteristics, and prognosis of such tumors continue to be debated.

Methods: A population-based series of 4,643 new cases of colorectal adenocarcinomas diagnosed between 1976 and 1996 in C te d'Or, France, was used to describe time trends in incidence, predisposing conditions, location, stage, and treatment and to evaluate the prognosis of such tumors in patients under 45 years of age (n = 146). Prognosis was determined using relative survival rates and predictive factors using a multivariate relative survival model.

Results: Before the age of 45 years, age-standardized incidence rates were 1.9 per 100,000 in males and 1.4 per 100,000 in females. Incidence rates almost doubled from 1976 to 1982 and from 1983 to 1989 in both genders and stabilized thereafter. The frequency of predisposing conditions was significantly higher before the age of 45 years (11.7 vs. 0.4 percent; P < 0.001). TNM Stage III tumors were more frequent in younger patients, and Stage II tumors were more frequent in older patients. The postoperative mortality rate was lower in the 0-to-44 age group, 2.1 percent, compared with 8.4 percent for the 45-and-over age group (P = 0.004). Five-year relative survival rates were 51.9, 49.2, and 41.4 percent, respectively. In both overall and stage-for-stage comparisons, patients before the age of 45 years had a better survival rate than older patients. Gender and stage at diagnosis were the only independent prognostic factors of survival for young patients.

Conclusions: This study confirms the high frequency of predisposing conditions in young patients and that young age is not a poor prognostic factor for colorectal cancer. This underlines the importance of family screening, aggressive surveillance, and treatment in the young with known predisposing conditions.