Distant recurrence and margin involvement in invasive breast cancer

The effect of involved margins after breast cancer surgery on distant recurrence (DR) is unknown. We determined the association between margin width or involvement, DR and cancer deaths.

Greater Manchester (GM) and the National Cancer Registry (NCRAS) cohorts were analysed. Margin status after curative surgery was measured. Cox-proportional hazards investigated factors associated with LR, DR and breast cancer deaths.

In GM (2010-2014), 2295 (70.2%) patients had clear margins ( > 2 mm), 302 (9.2%) close (1-2 mm) and 673 (20.6%) involved ( < 1 mm) margins. 2030 patients underwent breast conservation surgery (BCS). After multivariable adjustment in BCS patients, involved margins had an increased hazard of DR (HR 1.73, 95% CI:1.03, 2.88, p = 0.037) and LR (HR 2.16, 95% CI:1.31, 3.58, p = 0.003). NCRAS data from 2010-2013 in 16,420 BCS patients included 3,913 patients (23.9%) with final margins <1 mm. There were 642 deaths (3.9%) after 80.2 months median follow-up: 5.6% in patients with final margins <1 mm and 3.4% with margins >1 mm. After BCS, in 5246 patients who underwent chemotherapy after BCS, involved margins <1 mm had a HR of 1.33 (CI 1.10-1.60, p = 0.003) for cancer death.

Margins >1 mm were associated with lower DR and cancer deaths. Guidelines should recommend a minimum margin clearance of 1 mm.