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Long-term mortality in a cohort study of 6 800 French breast cancer patients treated between 1954 and 1983

Purpose. To investigate the impact of initial tumour characteristics and loco-regional radiotherapy on long-term survival following breast cancer diagnosis. Methods and materials. This study was conducted among 6 800 French women from a cohort of 7 711 subjects diagnosed at the IGR with breast cancer between 1954 and 1983 and followed-up until January 2004. Overall mortality in the cohort was compared with that in the French general population using Standardized Mortality Ratios (SMR) and the Absolute Excess Risk (AER) estimated by Poisson regression. Results. During the 1954–2004 follow-up period, 5 436 women died. Mortality was 3.15-fold higher in the cohort than in the general female population in France. It decreased from 6.86 to 1.26 during the first 30 years of follow-up then rose again to 1.60. Both SMRs and AERs were more than 2-fold higher in women who had received radiotherapy during initial treatment than in those who had not, this difference being higher for women treated before 1976 than afterwards (p < 0.0001). They (SMRs and AERs) were also higher for subjects who had stage II, III or IV lesions than for those with less advanced tumours. Conclusion. The results of this study suggest that the excess deaths observed during the first two decades are closely linked to the initial clinical characteristics of the tumour and to radiotherapy. The late increase in mortality may be partially due to deleterious late effects of radiotherapy.