Mastectomy rates in relation to adoption of a margin guideline.

Abstract

508 Background: Surgery after initial lumpectomy to obtain a bigger negative margin is common and may lead to mastectomy. The impact of a 2014 consensus statement endorsing a minimal negative margin for invasive breast cancer on surgeon attitudes, re-excision rates, and final surgical procedure is uncertain. Methods: Women with stage I and II breast cancer diagnosed between 7/13–8/15 and reported to the Los Angeles and Detroit SEER registries were surveyed about 2 months post diagnosis, and 70% responded; 3729 comprise the analytic sample. All attending surgeons identified by the patients (n=489) were sent a questionnaire at the end of the patient survey period, and 376 (77%) responded. Pathology reports were reviewed for margin status. Multinomial regression models were used to assess trends. Results: The 67% initial lumpectomy rate was unchanged during the study. The final lumpectomy rate increased by 13% (to 65% from 52%) from 2013–2015, accompanied by a decrease in unilateral (to 18% from 27%) and bilateral (to 16% from 21%) mastectomy (p=0.002). Surgery after lumpectomy, both re-excision and mastectomy, declined by 16% (p<0.001). Pathology review showed no association between date of treatment and positive margins. Patient report of surgeon-recommended mastectomy after initial lumpectomy declined to 8% from 20% (p<0.001). 69% of surgeons endorsed a margin of no ink on tumor to avoid re-excision in ER+PR+ cancer and 63% for ER-PR- cancer. Surgeons treating >50 breast cancers annually were more likely to accept this margin than those treating <20 cases (p<0.001). Conclusions: Additional surgery after initial lumpectomy markedly decreased between 2013‒2015 after publication of a margin guideline endorsinga minimal negative margin. This resulted in a substantial increase in lumpectomy as the definitive surgical procedure, which illustrates that guidelines can be an effective, low-cost approach to addressing clinical controversies.