Prognosis of early-stage synchronous bilateral invasive breast cancer

BackgroundContradictory data exists concerning the prognosis of patients with synchronous bilateral breast cancer (SBBC). Most authors report a worse prognosis for SBBC patients compared to unilateral breast cancer (UBC) patients. There are a few studies that did not support these findings. This study gives a comprehensive picture of SBBC and tests the hypothesis that outcome of this entity is based on the tumor with the worse prognosis (reference lesion).Patients & methodsThe data of two prospective Swiss breast cancer databases covering a 20-year period (1990–2009) was reviewed. Forty-six cases of SBBC were identified. In 34 patients with early-stage SBBC, the reference lesions (defined as the tumor with the more advanced stage or, in cases where both tumors had the same stage, the larger tumor) were compared in a case-control approach with 100 patients having UBC (SBBC/UBC ratio = 1/3). The controls were matched for age, time of diagnosis, tumor size, axillary node status, histological grade and estrogen-receptor status. Differences in terms of survival curves were analyzed using the log rank test; the possible correlation between matched groups was evaluated by a frailty Cox model.ResultsThere were no significant differences in disease-specific survival between SBBC and its unilateral controls (HR, 0.932; 95% CI, 0.322–1.07; p = 0.90).ConclusionsThe prognosis of SBBC was determined by the reference lesion; the contralateral second tumor had no additional impact on outcome.