Residual disease after re-excision lumpectomy for close margins.

INTRODUCTION: While a positive margin after an attempt at breast conservation therapy (BCT) is a reason for concern, there is more controversy regarding close margins. When re-excisions are performed, there is often no residual disease in the new specimen, calling into question the need for the procedure. We sought to examine the incidence of residual disease after re-excision for close margins and to identify predictive factors that may better select patients for re-excision.
METHODS: Our IRB-approved prospective breast cancer database was queried for all breast cancer patients who underwent a re-excision lumpectomy for either close or positive margins after an attempt at BCT. Close margins are defined as < or =2 mm for invasive carcinoma and < or =3 mm for DCIS. Clinicopathologic features were correlated with the presence of residual disease in the re-excision specimen.
RESULTS: Three hundred three patients (32%) underwent re-operation for either close (173) or positive (130) margins. Overall, 33% had residual disease identified, 42% of DCIS patients and 29% of patients with invasive disease, nearly identical to patients with positive margins. For patients with DCIS, only younger age was significantly related to residual disease. For patients with invasive cancer, only multifocality was significantly associated with residual disease (OR 3.64 [1.26-10.48]). However, patients without multifocality still had a substantial risk of residual disease. DISCUSSION: The presence of residual disease appears equal between re-excisions for close and positive margins. No subset of patients with either DCIS or invasive cancer could be identified with a substantially lower risk of residual disease.