Diagnosis and management of ductal carcinoma in situ.

Ductal carcinoma in situ (DCIS) is a preinvasive form of breast cancer that has increased in incidence over the past 25 years, primarily as a result of mammographically detected microcalcifications. Inadequately treated DCIS carries a risk for evolving into the malignant phenotype; however, the magnitude and timeline for this risk are poorly defined. Treatment options include lumpectomy with or without breast irradiation and mastectomy. The overall survival rate is 96% to 98% with any of these strategies, but the risk of local recurrence (LR) is highest after lumpectomy alone. Breast irradiation can reduce this risk from levels in excess of 40% to 10% over a 10-year follow-up period. Approximately 50% of all LR from DCIS are invasive lesions. Therefore, the occurrence of a LR after breast-conserving therapy is a potentially greater threat to the patient with DCIS compared to the patient diagnosed with invasive cancer. In patients diagnosed with invasive cancer, the risk of micrometastatic disease is present from the time of initial diagnosis. In patients with DCIS, the expectation is that a potentially 100% cure rate should be achieved with local therapy alone. Although most DCIS cases complicated by LR will be successfully salvaged with prolonged overall survival, it is critically important to take every precaution that will minimize the risk of locally recurrent disease. Therefore, radiation therapy as an adjunct to lumpectomy is essential. A subset of patients with DCIS with low-volume low-grade disease who can be safely treated by lumpectomy alone has not yet been clearly defined. Prospective studies designed to identify this category are ongoing. Inadequate margin control is the most consistent risk factor for LR that has been reported thus far, but there is no universally accepted definition for what constitutes an optimal negative margin distance. Young age at diagnosis, high nuclear grade, and comedonecrosis are other factors that have been implicated as increasing the risk for LR. Tamoxifen can further decrease the rate of new in-breast events on the affected side and in the contralateral breast. Ongoing trials will also define the role of aromatase inhibitors as a risk-reducing strategy.