Routine Margin Shaving Of Lumpectomy Cavity During Breast Conserving Surgery Detects Occult Multifocal Cancer, A Prospective Study

Background:  Cavity shaving (CS) entails circumferential tissue removal from residual lumpectomy cavity following tumor resection during breast conserving surgery (BCS). It could allow detection of occult multifocal breast cancer (OMFBC).
Objectives: This study aimed to highlight the impact of unidentified OMFBC as essential risk factor for local recurrence after BCS. 
Patients and Methods: Eligible breast cancer patients for BCS and CS were prospectively enrolled. Patients with negative margins of “resected tumor specimens” were designated as group A whereas group B comprised those with positive margins. OMFBC, diagnosed in the additionally shaved margins of the “residual lumpectomy cavity” as malignant breast tissues with intervening normal areas, was investigated in both groups. The study was conducted through the period from November, 2017 to March, 2021.
Results: Forty-two patients with median age of 43 years were studied. Group A included 32 patients (76.2%) compared with 10 (23.8%) in group B. Overall, OMFBC was confirmed in the additionally shaved margins in 6 (14.3%) patients. OMFBC rate was less in group A (4/32 patients, 12.5%) compared to B (2/10 patient, 20%), however the difference did not reach statistical significance. In group B, another 1 patient showed persistent positive margins without evidence of OMFBC. All 7 patients with positive CS margins (6 with OMFBC and 1 with persistent positive margin without evidence of OMFBC) had their treatment strategy switched to modified radical mastectomy. Local recurrence occurred in only one among the remaing 35 patients (2.9%) who were treated by BCS with CS.
Conclusions: CS improves outcome of BCS by reducing the rate of positive margins, enabling diagnosis of occult multifocal breast cancer and reducing local recurrence.