Pathologic margin involvement and the risk of recurrence in patients treated with breast-conserving therapy

BACKGROUND. The relationship between the microscopic margins of resection and ipsilateral breast recurrence (IBR) after breast-conserving therapy for carcinomas with or without an extensive intraductal component (EIC) has not been adequately defined. METHODS. Of 1,790 women with unilateral clinical Stage I or II breast carcinoma treated with radiation therapy as part of breast-conserving therapy, 343 had invasive ductal histology evaluable for an extensive component (EIC), had inked margins that were evaluable on review of the pathology slides, and received ≤60 Gray to the tumor bed; these 343 women constitute the study population. The median follow-up was 109 months. All available slides were reviewed by one of the study pathologists. Final inked margins of excision were classified as negative >1 mm (no invasive or in situ ductal carcinoma within 1 mm of the inked margin); negative ≤ 1 mm, or close (carcinoma ≤ 1 mm from the inked margin but not at the margin); or positive (carcinoma at the inked margin). A focally positive margin was defined as invasive or in situ ductal carcinoma at the margin in three of fewer low-power fields. The first site of recurrent disease was classified as either ipsilateral breast recurrence (IBR) or distant metastasis/regional lymph node failure. RESULTS. Crude rates for the first site of recurrence were calculated first for all 340 patients evaluable at 5 years, then separately for the 272 patients with EIC-negative cancers and the 68 patients with EIC-positive cancers. The 5-year rate of IBR for all patients with negative margins was 2%; and for all patients with positive margins, the rate was 16%. Among patients with negative margins, the 5-year rate of IBR was 2% for all patients with close margins (negative ≤ 1 mm) and 3% for those with negative > 1 mm margins. For patients with close margins, the rates were 2% and 0% for EIC-negative and EIC-positive tumors, respectively; the corresponding rates for patients with negative margins > 1 mm were 1% and 14%. The 5-year rate of IBR for patients with focally positive margins was 9% (9% for EIC-negative and 7% for EIC-positive patients). The 5- year crude rate of IBR for patients with greater than focally positive margins was 28% (19% for EIC-negative and 42% for EIC-negative and 42% for EIC-positive patients). CONCLUSIONS. Patients with negative margins of excision have a low rate of recurrence in the treated breast, whether the negative margin is > 1 mm or ≤ 1 mm and whether the carcinoma is EIC- negative or EIC-positive. Among patients with positive margins, those with focally positive margins have a considerably lower risk of local recurrence than those with more than focally positive margins, and could be considered for breast-conserving therapy.