Multicentric and Contralateral Invasive Tumors Identified with Pre-op MRI in Patients Newly Diagnosed with Ductal Carcinoma In Situ of the Breast

Abstract: Preoperative breast MRI in newly diagnosed cancer patients has several potential benefits. Improved survival for patients with invasive disease as the index lesion is unlikely to be one of these benefits, given what is known from variations in locoregional management in the historic conservation trials. However, this may not be the case for patients with ductal carcinoma in situ (DCIS), as the discovery of unsuspected invasive cancer located elsewhere from the biopsy‐proven DCIS could result in decreased survival if left undetected and untreated. In support of this hypothesis, a previous observational study of a large cohort of DCIS patients revealed the development of invasive cancer to be the most common event after unilateral DCIS treatment, occurring in 3.9%, mostly in the opposite breast. These cancers appeared on mammography or clinical exam within a short time frame (median 2.9 years) and were associated with a diminution in survival. Given these second events occurring so soon after DCIS treatment, it must be considered that invasive cancers were present elsewhere, but mammographically occult, at the time of DCIS diagnosis. To examine this possibility, 288 consecutive patients with newly diagnosed DCIS underwent preoperative MRI, with the discovery of separate foci of invasive cancer, either multicentric or contralateral, occurring in 3.5% of patients, a similar incidence to the short‐term observational study. These “elsewhere” invasive cancers are presented here with details of pathology such that both Stage I and Stage II disease can be seen as clinically significant, with the usual stage‐based survival implications.