Information provided by this trial has been supplemented with that provided by the available non-randomised evidence. Non-randomised studies provide descriptive information on outcomes associated with the treatments used, but are not necessarily able to answer the questions posed on treatment effectiveness. The most important prognostic factors for local recurrence are margin involvement and moderate or marked comedo necrosis. Other factors implicated in local recurrence include lesion size, mode of presentation, mammographic appearance, multifocality and multicentricity, estrogen receptor status, family history, and menopausal status. Evidence on the importance of these factors is, however, weak.
Mastectomy is a disfiguring procedure.
Invasive breast cancer detected early may often be adequately treated with less radical procedures. Consequently, the appropriate use of mastectomy in the management of DCIS remains unclear, although it is often considered for patients with extensive disease. There are no ongoing randomised trials addressing this issue. Radiation therapy is, however, associated with some toxicity. There is also a lack of reliable evidence of any reduction in risk resulting from treatment with radiotherapy on distant relapse or death from breast cancer, the risk of both being very small.