Similar rates of residual disease in patients with DCIS within 2 mm of lumpectomy margin regardless of the presence of invasive carcinoma

Purpose The 2014 Society of Surgical Oncology/American Society for Radiation Oncology (SSO/ASTRO) breast-conserving surgery (BCS) margin guidelines for invasive cancer recommended “no ink on tumor” as an adequate margin width. However, 2016 SSO/ASTRO margin guidelines for pure DCIS recommended a 2 mm margin. Thus, management of a margin with DCIS > 0 mm but < 2 mm differs based on presence or absence of invasive carcinoma. We compared rates of residual disease in patients with pure DCIS to patients with invasive cancer with DCIS. Methods BCS with complete shaved cavity margins (SCM) for invasive carcinoma or pure DCIS from 2004 to 2006 at our institution was reviewed. Margin width was measured on the main specimen and the presence of carcinoma in the SCM was used as a surrogate for residual disease in the cavity. Rates of residual disease were determined for varying margin widths of invasive carcinoma and DCIS. Results Of 329 BCS patients, 123 (37%) patients had pure DCIS and 206 (63%) had invasive cancer with DCIS. In the pure DCIS cohort, 61 patients had DCIS between 0 and 2 mm from the inked margin; 32 (52%) of which had residual disease in the SCM. In the invasive cancer plus DCIS cohort, 92 had DCIS between 0 and 2 mm from the inked margin; 39 (42%) of which had residual disease in the SCM ( p = 0.221). Conclusion Rates of residual disease are similar in patients treated with lumpectomy for pure DCIS and those with invasive carcinoma with DCIS when DCIS is found between 0 and 2 mm from the inked margin.