Safe negative margin width in breast conservative therapy: results from a population with a high percentage of negative prognostic factors.

Background: There remains a controversy in the literature regarding adequate width of negative surgical margins in breast conservative therapy (BCT). It is now advocated that no tumor on an inked margin is a safe negative margin. Majority of studies on the outcomes of BCT had patients with favorable prognostic factors. Pakistani population has a high expression of unfavorable prognostic factors. The objective of this study was to determine a safe negative margin width in Pakistani population that undergoes BCT.
Methods: A total of 603 patients with identifiable surgical margins underwent BCT from 1997 to 2009 in Shaukat Khanum Cancer Hospital. Patients were divided into close (≤2 mm), free (>2-10 mm), and wide (>10 mm) margin groups. Locoregional recurrence was defined as recurrence within the operated breast, ipsilateral axilla, or supraclavicular or internal mammary lymph nodes. Locoregional recurrence-free survival was calculated from the date of surgery to the date of locoregional recurrence. Five-year locoregional recurrence-free survival was determined for margin groups. Univariate and multivariate Cox proportional hazard analyses were performed to determine independent predictors of locoregional recurrence.
Results: A total of 415 (69 %) patients were <50 years of age. There were 82 (15 %) T3/T4, 337 (56 %) poorly differentiated, and 238 (39 %) ER/PR -ve tumors. Nodal positivity was present in 314 (52 %) patients. The actual number of locoregional recurrences was 16 (12 %), 8 (3 %), and 10 (4.6 %), respectively (P = 0.002). Expected 5-year locoregional recurrence-free survival was 90, 97, and 96 %, respectively (P = 0.002). On multivariate analysis, tumor size, nodal involvement, and negative margin width were independent predictors of locoregional recurrence.
Conclusion: A negative margin width of 2 mm might represent an adequate negative margin width in the Pakistani population undergoing breast conservative therapy.