Influence of Margin Status on Outcomes in Lobular Carcinoma: Experience of the European Institute of Oncology

Objective: We analyzed 382 patients with pure lobular carcinoma treated up to 2002 with sufficient follow-up to draw prognostic conclusions, all treated by conservative surgery. Our aim was to evaluate the influence of margin status on outcomes with a view assessing the appropriateness of conservative surgery in this breast cancer subtype. Methods: We assessed locoregional relapse, distant metastasis, contralateral breast cancer, breast cancer-related event free survival, disease-free survival and overall survival according to margin status categorized as at least 10 mm versus less than 10 mm (usually considered negative). Results: The proportions of patients with less than 10 mm margins varied significantly with age (P = 0.02), menopausal status (P = 0.006), and tumor size (P = 0.02) but no other characteristic was significantly related to margin status. As regards unfavorable events during follow-up, none differed significantly between at least 10 mm and less than 10 mm margin groups. In particular, there were 11 (3.7%) local relapses in the same quadrant in at least 10 mm margin group compared to 4 (4.6%) in the less than 10 mm margin group, and 7 (2.4%) ipsilateral breast cancers in the 10 mm or more margin group but none in the less than 10 mm group. These findings indicate that minimal residual disease as evidenced by margins less than 10 mm is eradicated by radiotherapy (backed up in selected cases by reexcision, which in this series was always conservative). The rate of contralateral breast cancer was low at 2.9% indicating that prophylactic contralateral mastectomy is not justified. Conclusions: We conclude that the surgical approach and criteria for adjuvant hormonal and systemic treatment in lobular carcinoma should be the same as for ductal carcinoma, provided that adequate preoperative investigations exclude extensive multifocal and contralateral disease.