Preoperative breast MRI in management of patients with needle biopsy-proven ductal carcinoma in situ (DCIS).

Background: In 20-25% of patients with biopsy-proven DCIS underestimation occurs. Sentinel lymph node biopsy (SLNB) is offered to patients with biopsy-proven ductal carcinoma in situ (DCIS) and a high risk of occult invasive cancer. However, assessment of high risk is controversial. We aimed to improve selection of patients for SLNB with preoperative breast magnetic resonance imaging (MRI).

Methods: In this prospective observational study, MRI was offered to all subsequent patients with a biopsy-proven DCIS admitted to a large Dutch teaching hospital between April 2012 and March 2017. MRI images were analysed for signs of invasive cancer and the results were compared with the pathologic results after surgical treatment. The diagnostic accuracy of additional MRI in detecting occult invasive cancer was determined.

Results: Of 211 patients eligible for additional MRI analysis, 149 underwent breast MRI. The majority (67%) received breast-conserving therapy, and the underestimation rate was 20%. Subsequent to MRI analysis, 20 additional invasive diagnostic procedures were performed. Occult invasive cancer was suspected on MRI in 46 patients (31%) and was confirmed in 18 (12%). In this study, breast MRI had a sensitivity of 67%, a specificity of 77%, and a true negative rate of 91%.

Conclusion: Preoperative breast MRI cannot reliably predict the presence of invasive cancer in patients with biopsy proven DCIS. Therefore, it cannot be used to in the selection of patients for a SLNB.