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 pa tients with mammographically detected ductal carcinoma in situ (DCIS) of th e breast with breast-conserving therapy (BCT) to determine 10-year rates of local control and survival and to identify factors associated with local r ecurrence. METHODS. From January 1980 to December 1993, 132 breasts in 130 patients we re treated with BCT for mammographically detected DCIS at William Beaumont Hospital, Royal Oak, Michigan. All patients underwent an excisional biopsy, and 64% were reexcised. AU patients received postoperative whole-breast ir radiation to a median dose of 45.0 Gray (Gy) (range: 43.1-56.0 Gy). One hun dred 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). AU cases underwent complete p athologic 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 immed iately adjacent to the lumpectomy cavity and were designated as true recurr ences or marginal misses (TR/MM). Four patients (31%) had recurrence elsewh ere 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%, resp ectively. Multiple clinical, pathologic, and treatment-related factors were analyzed for association with ipsilateral breast failure or TR/MM. In mult ivariate analysis, only the absence of pathologic calcifications was signif icantly associated with ipsilateral breast failure. When specifically analy zed 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 nor significan tly predict for either TR/MM (P = 0.14) or ipsilateral breast failure (P = 0.19). CONCLUSIONS. In patients with mammographically detected DCIS treated with B CT, adequate excision of all DCIS prior to RT can result in improved rates of local control. However, margin status may not adequately predict complet e tumor extirpation. The volume of DCIS within 5 mm of the margin appears t o be a more reliable surrogate for the adequacy of excision. In addition, y oung patient age and the absence of pathologic calcifications are independe nt risk factors for the development of local recurrence. (C) 2000 American Cnncer Society.