Of the 469 patients, 213 also received postoperative radiation therapy. There were 75 local recurrences, 38 in patients who underwent excision only and 37 in patients treated with excision plus postoperative radiation therapy. The mean follow-up was 81 months. Only 3 of 133 patients with margins 10 mm wide or wider had a local recurrence, and there was no reduction in the probability of local recurrence with the addition of postoperative radiation therapy (relative risk 1.14, P = 0.92). The mean estimated probability of recurrence at 8 years was 0.04. Among patients with a margin of 1 to <10 mm, of the 124 who received no radiation therapy and the 100 who received radiation therapy, 23 and 15 respectively, developed a local recurrence (relative risk 1.49, P = 0.24). In contrast, in patients with a margin of less than 1 mm, of the 39 who received no radiation therapy and the 73 who received radiation therapy, 13 and 21, respectively, developed a local recurrence (relative risk 2.54, P= 0.01). The relative risks of recurrence did not change substantially after adjustments for tumor size, nuclear grade and the presence or absence of comedonecrosis.