Prognostic factors for residual occult disease in shave margins during partial mastectomy.

PURPOSE: Shave margins have been shown to decrease positive final margins in partial mastectomy. We investigated prognostic factors associated with residual disease in shave margins. METHODS: Patients with invasive breast carcinoma and ductal carcinoma in situ (DCIS) who had circumferential shave margins excised during lumpectomy were abstracted from a retrospective database from 2015 to 2018. We defined residual occult disease (ROD) as either (1) residual disease in a shave margin when the initial lumpectomy specimen had negative margins or (2) residual disease in a shave margin that did not correspond with the positive lumpectomy margin. We identified the frequency of ROD and conducted logistic regression analysis to identify associated prognostic factors. RESULTS: 166 Patients (139 invasive carcinoma, 27 DCIS) were included with median follow-up of 28 months (9-50 months). Residual occult disease existed in 34 (24.5%) with invasive carcinoma and 8 (29.6%) with DCIS. In univariate analyses of the invasive group, invasive lobular carcinoma and a positive initial, non-corresponding lumpectomy margin were predictive of ROD (OR 3.63, p = 0.04, OR 3.48, p = 0.003 respectively). In multivariate analysis, a positive lumpectomy margin remained significant, p = 0.007. No variables were associated with ROD in DCIS. CONCLUSION: Residual occult disease was shown to be a frequent event in this analysis of lumpectomy with circumferential shave margins. Having a positive initial lumpectomy margin was predictive of ROD in a non-corresponding margin. Surgeons should consider not being selective in their shave margins or margin of re-excision if shave margins were not obtained in their initial surgery.