Margin Re-excision and Local Recurrence in Invasive Breast Cancer: A Cost Analysis Using a Decision Tree Model

Background: SSO-ASTRO recently published guidelines defining adequate margins in breast conservation therapy (BCT) as no tumor on ink based on studies demonstrating little difference in local recurrence (LR) with wider margins. We hypothesize that not routinely re-excising close margins results in decreased costs without compromising care. Methods: Adecision tree model was developed for the management of margins after BCT for invasive cancer. Patients were compared among three margin status groups: positive, close (<= 2 mm) and negative (> 2 mm). Ten publications provided re-excision rates (RER) and LR rates. The model assumed 140,000 BCT/year. Sensitivity analyses determined the most cost-effective strategy. Surgical costs were estimated using 2013 Medicare reimbursement rates. Results: Re-excising close margins was significantly more costly than the alternative, $233.1 million versus $214.3 million, per year in the United States. Total surgical cost was most sensitive to re-excision of close margins-increasing the RER from 0% to 100% resulted in an $18.8 million cost difference. Conclusions: The strategy of re-excising close margins resulted in a predicted cost of $18.8 million per year. This does not include hospital costs, the cost of surgical complications after re-excision, and underestimates the potential savings by using Medicare reimbursement rates. (c) 2015 Wiley Periodicals, Inc.