The influence of margin width on local control of ductal carcinoma in situof the breast

Background Ductal carcinoma in situ is a noninvasive carcinoma that is unli kely to recur if completely excised. Margin width, the distance between the boundary of the lesion and the edge of the excised specimen, may be an imp ortant determinant of local recurrence, Methods Margin widths, determined by direct measurement or ocular micrometr y, and standardized evaluation of the tumor for nuclear grade, comedonecros is, and size were performed on 469 specimens of ductal carcinoma in situ fr om patients who had been treated with breast-conserving surgery with or wit hout postoperative radiation therapy, according to the choice of the patien t or her physician. We analyzed the results in relation to margin width and whether the patient received postoperative radiation therapy. Results The mean (+/-SE) estimated probability of recurrence at eight years was 0.04+/-0.02 among 133 patients whose excised lesions had margin widths of 10 mm or more in every direction. Among these patients there was no ben efit from postoperative radiation therapy. There was also no statistically significant benefit from postoperative radiation therapy among patients wit h margin widths of 1 to <10 mm. In contrast, there was a statistically sign ificant benefit from radiation among patients in whom margin widths were le ss than 1 mm. Conclusions Postoperative radiation therapy did not lower the recurrence ra te among patients with ductal carcinoma in situ that was excised with margi ns of 10 mm or more. Patients in whom the margin width is less than 1 mm ca n benefit from postoperative radiation therapy. (N Engl J Med 1999;340:1455 -61.) (C) 1999, Massachusetts Medical Society.