The long-term outcome of synchronous bilateral breast cancer is worse than metachronous or unilateral tumours.

AIM There is uncertainty in the literature as to whether bilateral breast cancer carries a worse prognosis than unilateral disease because some studies suggest that the development of a second primary does not influence survival, while others report a decreased survival in patients suffering from bilateral disease. METHODS A prospectively accrued and regularly validated database of 1945 patients with breast cancer treated in a district general hospital between 1963 and 1999 was analysed for clinical and pathological tumour characteristics including family history, grade, type of tumour, treatment and outcome. RESULTS Five per cent of patients (92) suffered from metachronous and 43 (2%) from synchronous bilateral breast cancer. A family history of breast cancer was more common in patients with metachronous bilateral breast cancer (38%), compared with the unilateral group (15%) and the synchronous bilateral breast cancer group (17%) (chi(2)=22.9, P<0.001). Patients with synchronous bilateral breast cancer had a significantly worse overall survival when compared with those with metachronous bilateral or unilateral breast cancer (log-rank test chi(2)=6.1, P=0.047). CONCLUSION Women with metachronous breast cancer were more likely to have positive family history, while those with synchronous bilateral breast cancer tend to have shorter survival when compared with those with unilateral breast cancer. Synchronous bilaterality is not, however, an independent risk factor on multivariate analysis.