A new study presented at the American Society of Clinical Oncology Meeting has reported that rates of local recurrence after lumpectomy are significantly lower when clean surgical margins of at least 1 mm are achieved. The study included 4,832 women who underwent breast conserving surgery and radiotherapy at Centre François Baclesse, Caen, France between 1973 and 2002. Age, tumor size, histological subtype, grade, estrogen (ER) and progesterone receptor (PR) status, in situ component, axillary lymph node involvement, and initial tumor location all were taken into account. For the 2,569 women for whom it was known, initial margin status was classified as follows: positive, close (less than 1 mm), or negative (more than 1 mm). The women were followed for a median period of 71 months.

Cumulative incidence of local recurrence for the overall study group was found to be 5.3% at five years and 10.3% at 10 years. In single variable analysis, local recurrence was found to be influenced by margin status, age, subtype, grade, in situ component, ER and PR status, and axillary lymph node involvement. However, local recurrence was not influenced by the initial tumor location (the quadrant of the breast in which the tumor was found). The five-year local recurrence rate was found to be 2% among patients with negative surgical margins, 4.6% in those with close margins, and 9% for positive margins. It did not make a difference whether involved margins contained in situ (DCIS) or invasive cancer. Using multivariable analysis, factors associated with increased risk of local recurrence were found to be positive margins, young age (up to 40 years), negative hormone receptor status, and positive axillary lymph node status. The authors conclude that margin status is an important risk factor for local recurrence. Complete excision should be defined as having a clean margin with at least 1 mm of clearance.