Mammographically detected ductal carcinoma in situ treated with conservative surgery with or without radiation therapy: patterns of failure and 10-year results.

OBJECTIVE: The authors reviewed their institution's experience treating 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, patterns of failure, and factors associated with outcome. SUMMARY BACKGROUND DATA: From January 1980 to December 1993, 177 breasts in 172 patients were treated with BCT for mammographically detected DCIS of the breast at William Beaumont Hospital, Royal Oak, Michigan.
METHODS: All patients underwent an excisional biopsy, and 65% were reexcised. Thirty-one breasts (18%) were treated with excision alone, whereas 146 breasts (82%) received postoperative radiation therapy (RT). All patients undergoing RT received whole-breast irradiation to a median dose of 50.0 Gy. One hundred thirty-six (93%) received a boost to the tumor bed for a median total dose of 60.4 Gy. Median follow-up was 5.9 years for the lumpectomy alone group and 7.2 years for the lumpectomy + RT group.
RESULTS: In the entire population, 15 patients had an ipsilateral breast recurrence. The 5- and 10-year actuarial rates of ipsilateral breast recurrence were 7.8% and 7.8% for lumpectomy alone and 8.0% and 9.2% for lumpectomy + RT, respectively. Eleven of the 15 recurrences developed within or immediately adjacent to the lumpectomy cavity and were designated as true recurrences or marginal misses (TMM). Four recurred elsewhere in the breast. Eleven of the 15 recurrences were invasive, whereas 4 were pure DCIS. Only one patient died of disease, yielding 5- and 10-year actuarial cause-specific survival rates of 100% and 99.2%, respectively. Eleven patients were diagnosed with subsequent contralateral breast cancer, yielding 5- and 10-year actuarial rates of 5.1% and 8.3%, respectively. Clinical, pathologic, and treatment-related factors were analyzed for an association with ipsilateral breast failure or TR/MM. No factors were significantly associated with ipsilateral breast failure. In the entire population, the omission of RT and younger age at diagnosis were significantly associated with TR/MM. Patients younger than 45 years at diagnosis had a significantly higher rate of TR/MM in both the lumpectomy + RT and lumpectomy alone groups. None of the 37 patients who received a postexcisional mammogram had an ipsilateral breast failure versus 15 in the patients who did not receive a postexcisional mammogram.
CONCLUSIONS: Patients diagnosed with mammographically detected DCIS of the breast appear to have excellent 100-year rates of local control and overall survival when treated with BCT. These results suggest that the use of RT reduces the risk of local recurrence and that patients diagnosed at a younger age have a higher rate of local recurrence with or without the use of postoperative RT.