Breast-Conserving Surgeries With and Without Cavity Shave Margins Have Different Re-excision Rates and Associated Overall Cost: Institutional and Patient-Driven Decisions for Its Utilization

Surgical outcomes and costs associated with standard partial mastectomy with selective margin resection or standard partial mastectomy with cavity shave margins (CSM) were evaluated in matched patient cohorts. The CSM approach had significantly lower rates of positive margins and re-excisions and smaller tissue volumes excised. The higher initial surgical costs were partially offset by decreased re-excision rates. The results promote CSM implementation as a standard of care in breast-conserving surgery. Background: Reducing the rate of margin positivity and reoperations remains a paramount goal in breast-conserving surgery (BCS). This study assesses the effectiveness of standard partial mastectomy with cavity shave margins (CSM) compared with partial mastectomy with selective margin resection (SPM), with regard to outcomes of the initial surgeries, re-excisions, and overall costs. Patients and Methods: This is a retrospective review of 122 eligible breast cancer patients who underwent BCS at one institution. The CSM and SPM groups each included 61 patients, matched for presurgical diagnoses and clinical stage. Data including margin status, rates and reason for re-excision, associated operation times, and costs were analyzed. Results: Patients undergoing CSM had less than half the rate of positive margins (PMs) (10% vs. 23%; P = .03) and re-excisions (8% vs. 23%; P = .02) compared with SPM. In the former group, the margin involvement was focal, and re-excisions were performed almost exclusively for PMs. For SPM, the majority (92%) of PMs were on the main lumpectomy specimen rather than the selective margins, and re-excisions included, in addition to PMs, extensive or multifocal negative but close margins. Reduced breast tissue volumes were removed with CSM, particularly for patients undergoing a single surgery (47 vs. 165 cm(3); P < .001). The initial surgery with CSM is on average 27% more costly than that for SPM (P < .001), due to the increased pathology costs which are partially offset by the increased re-excision rates in SPM. Conclusion: Circumferential cavity shaving, associated with consistent lower PMs, tissue volumes excised, and re-excision rates, is appropriate for routine implementation as a method offering superior surgical outcomes.