Rates of margin positive resection with breast conservation for invasive breast cancer using the NCDB

Previous studies suggest the rate of positive surgical margin (PSM) after lumpectomy for breast cancer is approximately 20 %. The risk of PSM at time of resection is often a source of fear for patients, driving some to elect to undergo mastectomy. This study describes rates and predictors of positive margins for invasive breast cancers in the National Cancer Database (NCDB).

From 2004 to 2013, patients with non-metastatic invasive breast cancers who underwent breast conservation surgery were identified from the NCDB. Patients' demographic, clinical, and facility of treatment characteristics were collected and compared. Per SSO-ASTRO-ASCO criteria, margin negative is defined as no gross or microscopic disease (i.e. no tumor on ink). Bivariate tests and multivariate logistic regression were conducted to identify independent predictors of patients with PSM at the time of resection.

A total of 707,798 patients were identified with non-metastatic invasive breast tumors who underwent lumpectomy. Rate of PSM across the entire cohort was 5.02 %. Over time, the rate of PSM decreased significantly from 6.54 % in 2004 to 3.91 % in 2013 (p < 0.001). Pure lobular histology predicted for the highest rate of PSM compared with IDC (8.63 vs 4.55 %; p < 0.001). In adjusted analysis, high grade, non-ductal histology and HER2 amplification were significantly associated with PSM with breast conservation while estrogen and progesterone status were not.

This study demonstrates a 5 % risk of PSM at time of breast conservation surgery using a large, modern national database. Patients with invasive lobular and mixed histology have a nearly two-fold risk of PSM compared to invasive ductal cancers. These results provide important data points to help appropriately counsel patients regarding the risk of PSM.