Extent of excision margin width required in breast conserving surgery for ductal carcinoma in situ

Breast conserving surgery (BCS) is common practice for unifocal ductal carcinoma in situ (DCIS) less than 4 cm in size, but the extent of tumor free margin width around DCIS necessary to minimize recurrence is unclear.

Clinical and pathologic details were recorded from all patients with pure DCIS < 4 cm in size, treated with BCS between 1978 and 1997. Histologic margins were measured by using an ocular micrometer. Patients with clear margins (> 1 mm) were divided up into 3 groups for analysis based on margin of normal tissue excised: 1.1-5 mm, 5.1-10 mm, and 10.1-40 mm.

There were 66 patients with close margins (< or = 1 mm), of which 25 cases (37.9%) recurred. The recurrence rates for the 3 clear margin groups ranged from 4.5-7.1%. Median followup was 47 months (range 12-197 mos). Risk of recurrence in the group with close margins was greater than the subgroups with clear margins (P < 0.001); no differences in recurrence was seen between the individual subgroups with clear margins. Nuclear Grade 3 was predictive of recurrence (P = 0.03). Following excision alone, the recurrence rate was 18.6%, compared with 11.1% when radiotherapy was given as adjuvant therapy. Women with clear margins following excision had a recurrence rate of only 8.1%.

After BCS for DCIS, close margins were associated with a high risk of local recurrence. Radiotherapy did not compensate for inadequate surgical clearance.