Survival and age at diagnosis of breast cancer in a population-based cancer registry.

From the population covered by the Lombardy Cancer Registry, Italy, 1991 female breast cancer patients diagnosed from 1976 to 1981 were followed up until May 1987. Relative survival was 69% at 5 years and 58% at 10 years; median survival was 8.8 years. Ages 40-49 showed the best survival; ages 25-34 were 20% lower. From age 50 onwards, survival decreased progressively, with the exception of age group 65-74. We suggest that the best prognosis for ages 40-49, followed by the survival fall in subsequent ages, could be related to an anticipation of diagnosis in ages near menopause. The death hazard function showed a bimodal pattern, with a first peak in the first years after diagnosis, and a second one between the seventh and eighth years. The death hazard rate decreased by about 1% per year at each subsequent calendar year of diagnosis. When such an estimated calendar effect was taken in account, there were no considerable survival differences among Western countries covered by population-based cancer registries.