A close or positive margin after mastectomy is not an indication for chest wall irradiation except in women aged fifty or younger.

INTRODUCTION: Indications for postmastectomy radiation include primary tumor size > or = 5 cm and/or > or = 4 positive axillary nodes. In clinical practice, patients with a close or positive margin after mastectomy are also often treated with postmastectomy radiation. However, there is little data regarding the risk of a chest wall recurrence in patients with close or positive margins who otherwise would be considered low risk (tumor size <5 cm and/or 0-3 positive nodes). To address this issue, we assessed the risk of a chest wall recurrence in women with Stage I-II breast cancer who underwent mastectomy and were found to have primary tumor size <5 cm and 0-3 positive nodes with a close or positive deep margin. METHODS AND MATERIALS: The pathologic reports from 789 patients treated by mastectomy between 1985 and 1994 at our institution were retrospectively reviewed. Of these, 136 (17%) had tumor within 1 cm of the deep resection margin. The study population consists of 34 of these patients with close or positive margins whose primary tumor size was <5 cm with 0-3 positive axillary nodes and who received no postoperative radiation. The median age was 43 years (range 29-76). Of these, 44% had T1 tumors and 56% T2 tumors. Pathologic axillary nodal status was negative in 65% and positive in 35%. The median number of positive nodes was 1. The deep margin was positive in 2 patients, < or = 2 mm in 17 patients, 2.1-4 mm in 7 patients and 4.1-6 mm in 8 patients. Of the 34 patients, 67% received adjuvant chemotherapy +/- tamoxifen and 21% received tamoxifen alone. The median follow-up was 59 months (range 7-143).
RESULTS: There were 5 chest wall recurrences at a median interval of 26 months (range 7-127). One was an isolated first failure, one occurred concurrent with an axillary recurrence, and three were associated with distant metastases. The 5- and 8-year cumulative incidences of a chest wall recurrence were 9% and 18%. Patient age correlated with the cumulative incidence of chest wall recurrence at 8 years; age < or = 50 years had a rate of 28% vs. 0% for age >50 (p = 0.04). There was no correlation with chest wall failure and number of positive nodes, ER status, lymphovascular invasion, location of primary, grade, family history, or type of tumor close to the margin. Of 5 chest wall failures, 4 were in patients who had received adjuvant systemic chemotherapy +/- tamoxifen. Chest wall failures occurred in 1 patient with a positive deep margin, 3 patients with margins within 2 mm, and 1 patient with a margin of 5 mm. The estimated cumulative incidence probability of chest wall recurrence at 8 years by margin proximity was 24% < or = 2 mm vs. 7% 2.1-6 mm (p = 0.36), and by clinical size 24% for T2 tumors vs. 7% for T1 (p = 0.98).
CONCLUSIONS: A close or positive margin is uncommon (< or = 5%) after mastectomy in patients with tumor size <5 cm and 0-3 positive axillary nodes but, when present, it appears to be in a younger patient population. The subgroup of patients aged 50 or younger with clinical T1-T2 tumor size and 0-3 positive nodes who have a close (< or = 5 mm) or positive mastectomy margin are at high risk (28% at 8 years) for chest wall recurrence regardless of adjuvant systemic therapy and, therefore, should be considered for postmastectomy radiation.