Stage at diagnosis is a key explanation of differences in breast cancer survival across Europe.

We used multiple regression models to assess the influence of disease stage at diagnosis on the 5-year relative survival of 4,478 patients diagnosed with breast cancer in 1990-1992. The cases were representative samples from 17 population-based cancer registries in 6 European countries (Estonia, France, Italy, Netherlands, Spain and UK) that were combined into 9 regional groups based on similar survival. Five-year relative survival was 79% overall, varying from 98% for early, node-negative (T1N0M0) tumours; 87% for large, node-negative (T2-3N0M0) tumours; 76% for node-positive (T1-3N+M0) tumours and 55% for locally advanced (T4NxM0) tumours to 18% for metastatic (M1) tumours and 69% for tumours of unspecified stage. There was considerable variation across Europe in relative survival within each disease stage, but this was least marked for early node-negative tumours. Overall 5-year relative survival was highest in the French group of Bas-Rhin, Côte d'Or, Hérault and Isère (86%), and lowest in Estonia (66%). These geographic groups were characterised by the highest and lowest percentages of women with early stage disease (T1N0M0: 39% and 9%, respectively). The French, Dutch and Italian groups had the highest percentage of operated cases. The number of axillary nodes examined, a factor influencing nodal status, was highest in Italy and Spain. After adjusting for TNM stage and the number of nodes examined, survival differences were greatly reduced, indicating that for these women, diagnosed with breast cancer in Europe during 1990-1992, the survival differences were mainly due to differences in stage at diagnosis. However, in 3 regional groups, the relative risks of death remained high even after these adjustments, suggesting less than optimal treatment. Screening for breast cancer did not seem to affect the survival patterns once stage had been taken into account.