Influence of stage at diagnosis on survival differences for rectal cancer in three European populations.

Important differences have recently been highlighted between European countries in the survival of colorectal cancer patients. As data on stage at diagnosis were available for rectal cancers in three European population-based registries (Geneva Switzerland; Côte d'Or, France; Mallorca, Spain), we compared relative survival while assessing the effect of stage in a multiple regression model. We analysed 1005 rectal cancer cases diagnosed between 1982 and 1987 and followed up for at least 5 years. In the Mallorca registry, 16% of the patients were diagnosed in the TNM stage I (versus 21% in the Côte d'Or registry and 29% in the Geneva registry, P < 10(-4)) and the 5-year relative survival rate was lower (35%) than in the other two registries (Côte d'Or 47%, Geneva 48%, P = 0.01). In the multivariate analysis, stage was the only independent prognostic factor, whereas the excess death risk did not vary significantly among registries (compared to Geneva, Côte d'Or relative risk was 1.0, Mallorca relative risk 1.11, 95% confidence interval 0.76-1.32 and 0.85-1.44 respectively). Survival differences between the registries were mainly due to stage at diagnosis. Thus, diagnostic conditions appear to be the main determinant of the survival inequalities found in those three European populations.