Long-term outcome after breast-conservation treatment with radiation for mammographically detected ductal carcinoma in situ of the breast.

Background: Ductal carcinoma in situ (DCIS) is detected most commonly on routine screening mammography in the asymptomatic patient, and has a long natural history. The objective of the current study was to determine the long-term outcome after breast-conservation surgery followed by definitive breast irradiation for women with mammographically detected DCIS of the breast.

Methods: In total, 1003 women with unilateral, mammographically detected DCIS of the breast underwent breast-conserving surgery followed by definitive breast irradiation. These women were treated in 10 institutions in North America and Europe. The median follow-up was 8.5 years (mean, 9.0 years; range, 0.2-24.6 years).

Results: The 15-year overall survival rate was 89%, and the 15-year cause-specific survival rate was 98%. The 15-year rate of freedom from distant metastases was 97%. In total, there were 100 local failures (10%) in the treated breast. The 15-year rate of any local failure was 19%, and the 15-year rate of local only first failure was 16%. Patient age > or = 50 years at the time of treatment and negative final pathology margins from the primary tumor excision both were associated independently with a lower risk of local failure in univariate analysis (P = 0.00062 and P = 0.024, respectively) and in multivariate analysis (P = 0.00057 and P = 0.0026, respectively). For favorable subgroups of patients age > or = 50 years or with negative resection margins, the 10-year risk of local failure was < or = 8%.

Conclusions: The current results support the use of breast-conserving surgery followed by definitive breast irradiation for the treatment of patients with mammographically detected DCIS of the breast. Patient age > or = 50 years at the time of treatment and negative resection margins both were associated independently with a decreased risk of local failure.