Cavity shaving halved the rates of positive margins and reexcision among patients undergoing partial mastectomy for breast cancer, a study published this week in The New England Journal of Medicine has shown.

The American Cancer Society estimates that there will be approximately 231,840 new cases of invasive breast cancer and 60,290 new cases of carcinoma in situ diagnosed in women in the United States in 2015.

For the study, researchers sought to determine whether resecting additional tissue surrounding the cavity left by partial mastectomy would decrease the rates of positive margins and reexcision.

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Researchers enrolled 235 patients with stage 0 to 3 breast cancer who were undergoing partial mastectomy, with or without resection of selective margins, and randomly assigned them 1:1 to have further cavity shave margins resected or not to have further cavity shave margins resected. Of those, 23% had invasive cancer, 19% had ductal carcinoma in situ, and 53% had both.

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Results showed that after partial mastectomy but prior to randomization, the rate of positive margins was 36% in the shave group and 34% in the no shave group (P=0.69); however, after patients were randomly assigned, the rate of positive margins was 19% and 34%, respectively (P=0.01).

Researchers also found that patients in the shave group had a lower rate of second surgery for margin clearance (10% vs. 21%; P=0.02). The study demonstrated no significant difference in complications between the two treatment arms.


  1. Chagpar AB, Killelea BK, Tsangaris TN, et al. A randomized, controlled trial of cavity shave margins in breast cancer.N Engl J Med. 2015; 373:503-510.