Abstract P3-09-03: Cost effectiveness analysis of approaches to axillary management in the setting of contralateral prophylactic mastectomy

Abstract Background: Occult malignancy (OM) found in contralateral prophylactic mastectomy (CPM) specimens presents challenges for axillary staging as post-mastectomy sentinel lymph node (SLN) surgery is not validated. No consensus exists on the optimal strategy for evaluating the axilla in this setting. Approaches include preoperative breast magnetic resonance imaging (MRI), selective SLN surgery determined by risk of OM, routinely performed SLN surgery, routinely omitted SLN surgery and selective SLN mapping for delayed SLN surgery using superparamagnetic iron oxide. Herein we evaluate the cost effectiveness of these strategies. Methods: A decision tree representing the possible choices and outcomes for axillary staging in the setting of OM in CPM was constructed. A literature review was conducted to determine event probabilities. For selective SLN mapping, a threshold of 7% preoperative risk of OM was based on previously identified risk factors. Cost data for surgical, anesthetic, pathology, and facility fees were obtained from FAIR Health. Quality-Adjusted Life Years (QALYs) were calculated using previously published values for the rate of lymphedema following axillary surgery, the associated health-related quality of life decrease, and expected survival following bilateral mastectomy. A cost-utility analysis was conducted to determine expected costs, impact on QALYs, and incremental cost effectiveness ratios (ICER) for each of the possible approaches relative to the historical standard, mastectomy followed by axillary dissection if occult malignancy is identified. A sensitivity analysis was performed to identify the risk threshold at which SLN mapping becomes cost effective. Results: The pooled rate of OM in the contralateral breast for women diagnosed with unilateral breast cancer was 1.89%. Costs ranged from $12,728 for mastectomy alone to $15,295 for routine preoperative MRI. Minor differences in QALYs were noted, ranging from 34.006 for preoperative MRI to 34.027 for preoperative risk assessment and SLN mapping, due to the low incidence of OM and low need for axillary dissection. Cost per QALY ranged from $374.04 for mastectomy alone to $449.77 for preoperative MRI. Preoperative MRI was the only strategy that was not cost effective relative to historical standard, yielding increased cost with decreased QALYs. The most cost-effective strategies included mastectomy with no additional axillary surgery, mastectomy with selective SLN mapping, and mastectomy with postoperative SLN surgery. On sensitivity analysis, risk assessment with selective SLN mapping remained cost effective across the expected levels of risk. Conclusions: Different strategies for axillary management for CPM yield minor differences in QALYs. Routine MRI is the least cost-effective strategy, resulting in highest cost and lowest QALY. Selective SLN surgery resulted in lower QALYs than no initial axillary staging or selective SLN mapping with no significant improvement in cost. Selective SLN mapping allows for axillary staging with an improvement in QALYs and lower cost and should be considered the optimal strategy for axillary staging in women undergoing CPM. Citation Format: Christopher Vetter, Judy C. Boughey, Jeffrey E. Johnson. Cost effectiveness analysis of approaches to axillary management in the setting of contralateral prophylactic mastectomy [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P3-09-03.