Abstract P4-11-07: The Oncotype DX® test to guide adjuvant chemotherapy treatment decisions for early node-negative HR+/HER2- breast cancer patients in Japan: a cost-effectiveness analysis

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Abstract Background: For patients with hormone-receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-), axillary lymph node-negative (N0) early-stage breast cancer, adjuvant chemotherapy treatment decisions are traditionally determined by clinico-pathological features. While the use of clinico-pathological features may provide useful prognostic information, it is not able to predict the benefit of adjuvant chemotherapy, which may lead to over- or undertreatment. The Oncotype DX Breast Recurrence Score® test has been reimbursed in Japan since September 2023, and to date, it is the only multigene assay with the ability to predict chemotherapy benefit validated by evidence from randomized clinical trials. The aim of the study was to estimate cost-effectiveness of guiding chemotherapy treatment decisions using the Oncotype DX® test compared to using clinico-pathological risk alone among women with N0 HR+/HER2- early breast cancer from a Japanese healthcare perspective. Methods: A previously published cost-effectiveness model built in Microsoft Excel estimated the cost-effectiveness of the Oncotype DX test compared to treatment decisions based on clinico-pathological risk alone over a lifetime horizon. This model used a decision tree coupled with a Markov model and was adapted to a Japanese healthcare payer perspective, complying with Japanese cost-effectiveness analysis guidelines. The N0 population was studied as a whole, as well as in subgroups based on age and clinico-pathological risk, defined according to tumour size and histologic grade. The modelled proportions of patients assigned to adjuvant chemotherapy and supportive treatment was informed by eight clinical experts in Japan to reflect current country-specific clinical practice. The Markov part of the model included health states representing recurrence-free, distant recurrence, death, as well as acute myeloid leukaemia (AML) and congestive heart failure (CHF) as latent adverse events of chemotherapy. The probability of distant recurrence of breast cancer conditional on test result category was derived from pivotal trials. Costs of testing, adjuvant and supportive treatment, disease management, and short-term adverse events were informed using Japanese cost sources. To assess uncertainty, deterministic and probabilistic sensitivity analyses were performed. Results: Using the Oncotype DX test was a dominant strategy compared to using clinico-pathological risk alone, with lower costs (-¥1,629,239) and additional health benefit (0.163 quality-adjusted life years, QALY) in the overall N0 population. This result was mainly driven by a reduced rate of distant recurrence for patients correctly treated with adjuvant chemotherapy after using the Oncotype DX test, which led to substantial cost savings and QALY gains. Probabilistic sensitivity analysis showed the Oncotype DX test was dominant against clinico-pathological risk alone in 99.4% of 5,000 simulations. Similar results were reported across subgroups; the Oncotype DX test was consistently cost-effective across all age and clinical subgroups considered, and was dominant (cost-saving and more effective) in 3 of 4 subgroups; in the subgroup aged≤50 with high clinical risk, the incremental cost-effectiveness ratio was ¥397,541/QALY. Conclusion: Using the Oncotype DX test to guide chemotherapy treatment decision for women with early-stage N0 HR+/HER2- breast cancer is expected to be cost saving and a cost-effective strategy in Japan. It is expected to yield substantial net costs savings in most of the subgroups considered while increasing QALYs gained from avoiding chemotherapy adverse events and distant recurrence. Citation Format: Kei Koizumi, Tobiasz Lemański, Gebra Cuyún Carter, Sebastien Eymere, Ataru Igarashi, Steve Millen, Mariko Nomoto, Yoshie Onishi, Vladislav Berdunov, Masamitsu Hihara, Aki Kudo, Pieter Drost, Naoki Niikura. The Oncotype DX® test to guide adjuvant chemotherapy treatment decisions for early node-negative HR+/HER2- breast cancer patients in Japan: a cost-effectiveness analysis [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 P4-11-07.

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