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Mastectomy was the standard treatment of DCIS through the first four decades of its recognition as a distinct histopathologic entity. Mastectomy is a highly effective treatment for DCIS, with a locoregional control rate of 96% to 100% and cancer-specific mortality rates of 4% or less (111). No randomized study has compared mastectomy with breast-conservation treatment for DCIS. Therefore, the relative outcomes for mastectomy and breast-conservation treatment can be estimated only by reviewing nonrandomized, retrospective studies. Local treatment failure after mastectomy (111) may occur because of unrecognized invasive carcinoma that results in local recurrence or distant metastasis, or it may be the result of incomplete removal of breast tissue with the subsequent formation of a new primary tumor.

Data from some surgical trials (45) and large treatment registries (35) suggest that the rates of local or regional recurrence are significantly lower after mastectomy than after breast-conserving surgery, but there have been no significant differences in overall survival. Metastatic breast cancer can follow the recurrence of an invasive tumor or the development of cancer in the contralateral breast. However, death related to breast cancer within 10 years after the diagnosis of DCIS occurs in only 1% to 2% of all patients, irrespective of whether mastectomy or breast-conserving surgery was performed (35).