Comparison of outcomes of breast conserving therapy in multifocal and unifocal invasive breast cancer

Background: There is controversy about whether breast conserving therapy (BCT) should be contraindicated in multifocal (MF) breast cancer. Few studies have reported on the oncologic safety of BCT in MF breast cancer.

Study design: We reviewed a prospective database of 1,169 women with invasive breast cancer who were treated with segmentectomy and whole breast irradiation from 1991 through 2009 and followed at our institution. Multifocal breast cancer was defined as 2 or more distinct tumors excised with a single incision or segmentectomy. We compared 2 groups, MF and unifocal breast cancer patients, with respect to demographics, tumor characteristics, adjuvant systemic therapy, local recurrence (LR), disease-free survival (DFS), and overall survival (OS).

Results: One hundred sixty-four patients with MF and 999 with unifocal invasive breast cancer were treated with BCT. Median follow-up was 112 months. Compared with the unifocal group, patients in the MF group had higher 10-year LR (0.6% vs 6.1%, p < 0.001) and lower 10-year DFS (97.7% vs 89.3%, p < 0.001) and OS (98.4% vs 85.8%, p < 0.001). On multivariable analysis, multifocality was independently significantly associated with local recurrence-free survival (LRFS), DFS, and OS.

Conclusions: Our data suggest that BCT in MF breast cancer is oncologically safe but may result in a slightly inferior outcome compared with BCT in unifocal breast cancer.