(S029) Evaluating the Role of a 21-Gene Expression Assay in Directing Adjuvant Radiotherapy Decisions for Elderly Women With Early-Stage Breast Cancer

Charles E. Rutter, MD, Nataniel H. Lester-Coll, MD, Suzanne B. Evans, MD, MPH; Department of Therapeutic Radiology, Yale University School of Medicine

OBJECTIVE: Adjuvant breast radiotherapy (RT) after breast-conserving surgery (BCS) in elderly women with early-stage breast cancer (ESBC) confers a local control benefit but no improvement in overall survival. Hence, the role of RT in this population is uncertain. In the separate context of adjuvant chemotherapy recommendations for node-negative ESBC, gene expression testing has allowed risk-adapted decision making and has had a marked impact on clinical practice. We sought to determine the potential role and cost-effectiveness of gene expression testing in directing adjuvant RT decisions for elderly ESBC patients, given a published relationship of Oncotype DX (ODX) results with local-regional recurrence risk.

METHODS: The distribution of ODX recurrence scores (RSs) among elderly women (aged ≥ 70 yr) with estrogen receptor–positive ESBC (pT1N0M0) post-BCS was defined within the National Cancer Data Base (NCDB), using standard definitions of low (< 18), intermediate (18–30), and high risk (> 30). Next, a decision tree was constructed to determine the overall cost-effectiveness of ODX in directing RT recommendations. Local-regional recurrence estimates at 10 years were extrapolated from the literature and assumed to be 1%, 3%, and 5% in patients with low, intermediate, and high RSs, respectively, following BCS, RT, and 5 years of tamoxifen. Rates of adjuvant radiotherapy utilization for each RS stratum were based upon published patterns of RS-guided adjuvant chemotherapy utilization.

RESULTS: We identified 2,564 elderly ESBC patients treated between 2007 and 2011 within the NCDB with ODX RS results. Median age and tumor size were 73 years (range: 70–90 yr) and 1.2 cm (range: 0.1–2 cm), respectively. Median RS was 15 (standard deviation [SD] = 8.3). RS was low, intermediate, and high in 69.2%, 28.3%, and 2.5% of patients, respectively. Neither age nor tumor size was associated with RS. ODX-directed adjuvant radiotherapy recommendations resulted in a net savings of $1,163.05 per patient and a utility decrease of 0.024 quality-adjusted life years (QALYs) relative to current clinical practice, yielding an incremental cost-effectiveness ratio for ODX-directed adjuvant radiotherapy of $47,920.78/QALY.

CONCLUSIONS: We observed a wide range of RSs among elderly ESBC patients in the NCDB. Further research is needed to determine if gene expression assays are capable of risk-stratifying within this population, as a means for directing adjuvant RT recommendations after BCS. Should this be proven, our findings would suggest that ODX-directed decision-making is theoretically cost-effective at a conservative willingness-to-pay threshold of $50,000/QALY.

Proceedings of the 97th Annual Meeting of the American Radium Society- americanradiumsociety.org