Purpose There is concern that women with multifocal ductal carcinoma in situ (DCIS; confined to one quadrant) who are treated with breast-conserving surgery face a high risk of local recurrence; therefore, many are treated with mastectomy. The objective of this study is to evaluate the significance of multifocality and the outcomes of women with multifocal DCIS treated with breast-conserving therapy. Methods The records of patients treated with breast-conserving surgery for DCIS between 1982 and 2000 were reviewed. Multivariate analyses were performed to evaluate the effects of multifocality and other prognostic factors on the rate of local recurrence. Results Of 615 cases of DCIS reviewed, 310 (41%) received breast-conserving surgery and 305 (40%) received breast-conserving surgery plus radiation (n = 260 with multifocality, n = 314 without multifocality, and n = 31 focality unreported). On multivariate analysis, multifocality (hazard ratio [HR] = 1.80; 95% CI, 1.15 to 2.80; P = .01), radiation treatment (HR = 0.46; 95% CI, 0.29 to 0.74; P = .001), margin width 4 mm or smaller (HR = 1.74; 95% CI, 1.03 to 2.92; P = .04), and high nuclear grade (HR = 1.65; 95% CI, 1.02 to 2.65; P = .04) were associated with risk of local recurrence. The detrimental effect of multifocality was limited to women who did not receive radiotherapy; the local recurrence–free survival rate at 10 years was 59% for women with multifocal disease and 80% for women without multifocality (P = .02). Among women treated with breast-conserving surgery plus radiation, there was no difference in 10-year local recurrence–free survival (80% v 87%; P = .35). There was no association between multifocality and the development of invasive recurrence. Conclusion Multifocality is a significant predictor of local recurrence in women who receive breast-conserving surgery for DCIS without radiotherapy; however, low recurrence rates can be achieved if adjuvant radiation is administered.
