HER-2 positive breast cancer is associated with an increased risk of positive cavity margins after initial lumpectomy

BACKGROUND: The effect of breast cancer subtype on margin status after lumpectomy remains unclear. This study aims to determine whether approximated breast cancer subtype is associated with positive margins after lumpectomy, which could be used to determine if there is an increased risk of developing local recurrence (LR) following breast-conserving surgery. METHODS: We studied 1,032 consecutive patients with invasive cancer who received lumpectomies and cavity margin (CM) assessments from January 2003 to November 2012. The following data were collected: patient age, cT stage, pT stage, grade, status of CM, lymph node status, menopausal status, ER, PR, HER-2, and Ki67, as well as the presence of extensive intraductal component (EIC) and lymphovascular invasion (LVI). A χ(2) test was used to compare categorical baseline characteristics. Univariate and multivariate logistic regression analyses were performed to evaluate associations between pathologic features of CM status. Kaplan-Meier actuarial cumulative rates of LR (ipsilateral in-breast) were calculated. RESULTS: A total of 7,884 pieces of marginal tissue were collected from 1,032 patients, and 209 patients had positive CMs. Of the patients tested, 52.3% had luminal A subtype, 14.9% were luminal B, 12.8% were luminal-HER-2, 8.1% were HER-2 enriched, and 11.8% were triple negative. Univariate analysis showed that EIC (P <0.001), LVI (P = 0.026), pN stage (N1 vs. N0: P = 0.018; N3 vs. N0: P <0.001), and luminal B (P = 0.001) and HER-2 (P <0.001) subtypes were associated with positive CMs. Multivariable analysis indicated that only EIC (P <0.001), pN stage (P = 0.003), and HER-2 subtype (P <0.001) were significantly correlated with positive CMs. On multivariable analysis, HER-2 subtype was an independent prognostic factor in LR (P = 0.031). CONCLUSIONS: The HER-2 subtype was the predictive factor most associated with positive CMs and an independent prognostic factor for LR. This result suggests that the increased risk of LR in HER-2 breast cancer is due to an increased microscopic invasive tumor burden, which is indicated by margin status after lumpectomy. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/1477-7819-12-289) contains supplementary material, which is available to authorized users.