Prediction of pathological margin status using preoperative contrast-enhanced MRI in patients with early breast cancer who underwent skin-sparing mastectomy.

Skin-sparing mastectomy (SSM) with immediate reconstruction is standard surgical treatment for early breast cancer with widespread ductal carcinoma in situ (DCIS). The local recurrence rate after SSM is up to 7.0%. We investigated prediction of the pathological margin using contrast-enhanced MRI, and evaluated the cut-off point to obtain the safety margin. We performed SSM with immediate reconstruction in 216 early breast cancer patients with widespread DCIS and/or invasive cancer from January 2014 to December 2015. Forty cases were retrospectively reviewed after excluding those with >15 mm between skin and tumor, determined by preoperative contrast-enhanced MRI, or involving reconstructive surgery for local recurrence, immeasurable lesion by preoperative contrast-enhanced MRI, or neoadjuvant chemotherapy. We defined a positive pathological margin as <1 mm from the cancer nest. We reviewed the distance between skin and tumor by MRI and pathological examination. To identify the cut-off for predicting a positive pathological margin, we performed sensitivity analysis using an ROC curve. The margin-positive rate by pathological examination was 27.5% (n = 11/40), with a moderate correlation of MRI margin and pathological margin (r = 0.44). The best cut-off point for margin positivity was 5 mm of MRI margin, with sensitivity and specificity of 54% and 86%, respectively (P = 0.009). This is the first prediction of pathological margin by preoperative contrast-enhanced MRI in early breast cancer patients with SSM. Care is required for SSM if the MRI margin is less than 5 mm due to pathological margin positivity.