Background: The clinical epidemiology of bilateral breast cancer was assessed in a population-based study from Saarland, Germany.
Methods: Clinical aspects of breast cancer, including age and tumor spread at diagnosis and survival, were compared between 251 patients with bilateral breast cancer and all 9585 patients with a first diagnosis of breast cancer registered with the population-based cancer registry of Saarland, Germany, between 1968 to 1987.
Results: The patients with bilateral breast cancer were on average considerably younger at the time of diagnosis of the first breast cancer than the total group of patients with breast cancer (mean age, 55.7 years versus 60.5 years). Overall, the distribution of tumor spread at diagnosis of the second breast cancers was similar to the corresponding distribution of first breast cancers, but a much less favorable distribution was observed among second breast cancers that developed in women younger than 50 years of age. The survival rates after diagnosis of a second breast cancer were much worse than the survival rates after a first breast cancer diagnosis. These differences persisted after control for important covariates such as age and tumor spread and were more pronounced if the first tumor was diagnosed in an advanced stage and if the time interval between diagnosis of the first and second cancers was short. Nevertheless, tumor spread at diagnosis of the second cancer was by far the most important predictor of survival among patients with bilateral breast cancer.
Conclusions: The differences in clinical aspects of first and second breast cancers should be considered in clinical management of patients with breast cancer. Further research is required to explain these differences.