Re-operation rates following breast-conserving surgery (BCS) for early invasive breast cancer are highly variable, largely due to uncertainty regarding adequate margins. The 2014 SSO-ASTRO guidelines recommended “no ink on tumor” as adequate margins. We evaluated the effect of guideline implementation on re-operation following BCS at our regional cancer center.

Retrospective chart review was performed on records for patients with early invasive breast carcinoma undergoing BCS between February 2011 and May 2017. Time period, pathologic margin status, patient and tumor characteristics were assessed for their impact on re-operation rates.

Overall re-operation rate decreased following the guidelines release (OR 0.28, 95% C.I. 0.15–0.51, p = <0.0001), with an unadjusted decrease of 3.89%. Re-operations on both close (OR 0.17, 95% C.I. 0.07–0.40, p = <0.0001) and widely negative (OR 0.20, 95% C.I. 0.05–0.77, p = 0.02) margins decreased in the post-guidelines time period.

SSO-ASTRO margins guideline release was associated with decreased re-operation. Furthermore, re-operations rates decreased in patients with pathologically negative margins, the target population the guidelines were meant to address.

This study found that implementation of the 2014 SSO-ASTRO invasive margin guidelines was associated with decreased odds of re-operation, as well as significantly decreased re-operation on patients with pathologically negative margins at a regional cancer center.