Factors associated with local recurrence of mammographically detected ductal carcinoma in situ in patients given breast-conserving therapy

BACKGROUND The authors reviewed their institution's experience treating patients with mammographically detected ductal carcinoma in situ (DCIS) of the breast with breast-conserving therapy (BCT) to determine 10-year rates of local control and survival and to identify factors associated with local recurrence. METHODS From January 1980 to December 1993, 132 breasts in 130 patients were treated with BCT for mammographically detected DCIS at William Beaumont Hospital, Royal Oak, Michigan. All patients underwent an excisional biopsy, and 64% were reexcised. All patients received postoperative whole-breast irradiation to a median dose of 45.0 Gray (Gy) (range: 43.1–56.0 Gy). One hundred twenty-four cases (94%) received a boost to the tumor bed for a median total dose of 60.4 Gy (range: 45.0–71.8 Gy). All cases underwent complete pathologic review by one pathologist. The median follow-up was 7.0 years. RESULTS Of the entire study group, 13 patients developed recurrence within the ipsilateral breast, for 5- and 10-year actuarial rates of 8.9% and 10.3%, respectively. Nine of the 13 recurrences (69%) occurred within or immediately adjacent to the lumpectomy cavity and were designated as true recurrences or marginal misses (TR/MM). Four patients (31%) had recurrence elsewhere in the breast. Ten of the 13 recurrences (77%) were invasive, whereas 3 (23%) were pure DCIS. Only 1 patient died of disease, corresponding to 5- and 10-year actuarial cause specific survival rates of 100% and 99.0%, respectively. Multiple clinical, pathologic, and treatment-related factors were analyzed for association with ipsilateral breast failure or TR/MM. In multivariate analysis, only the absence of pathologic calcifications was significantly associated with ipsilateral breast failure. When specifically analyzed for TR/MM, younger age at diagnosis, number of slides with DCIS, number of DCIS and cancerization of lobules (COL) foci within 5 mm of the margin, and the absence of pathologic calcifications demonstrated a statistically significant association. Close or positive margin status did not significantly predict for either TR/MM (P = 0.14) or ipsilateral breast failure (P = 0.19). CONCLUSIONS In patients with mammographically detected DCIS treated with BCT, adequate excision of all DCIS prior to RT can result in improved rates of local control. However, margin status may not adequately predict complete tumor extirpation. The volume of DCIS within 5 mm of the margin appears to be a more reliable surrogate for the adequacy of excision. In addition, young patient age and the absence of pathologic calcifications are independent risk factors for the development of local recurrence. Cancer 2000;88:596–607. © 2000 American Cancer Society.