Abstract P3-16-01: Population effectiveness model of the consequences of recurrence after trastuzumab emtansine (T-DM1) treatment among U.S. patients with high-risk HER2+ early-stage breast cancer (ESBC)

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Abstract Background: To estimate the long-term consequences of disease recurrence following treatment with adjuvant T-DM1 among U.S. patients with high-risk HER2+ ESBC who did not achieve pathologic complete response (pCR) after neoadjuvant therapy. Methods: A Markov model was used to simulate local/regional and distant recurrence with 10 years of follow-up. This corresponds to the estimated number of U.S. patients with incident high-risk HER2+ ESBC in 2021 (n = 10,000), which was derived from SEER population-based estimates, the NEOSPHERE trial and expert clinical opinion. The probability of recurrence was based on the T-DM1 arm in the KATHERINE trial and long-term results from the HERA trial. We assumed that 80% of patients with any recurrence experience distant recurrence, while the remainder have local/regional recurrence. SEER data and literature review were used to estimate probabilities of survival, distant recurrence secondary to local/regional recurrence, and direct medical costs. We estimated indirect costs were equal to 15% of direct medical costs. Model outcomes included: recurrences, breast cancer-related deaths, non-breast cancer-related deaths, direct medical costs, and indirect costs (all undiscounted). Results were compared to a scenario in which there was no recurrence to estimate population impact. All outcomes were also projected over 10 annual incident cohorts, each with 10 years of follow-up. Results: We estimated the 2021 U.S. patient cohort would experience 2,279 recurrences, including 1,834 distant, and 1,559 breast cancer-related deaths over 10 years, resulting in 7,744 lost years of life and $632 million in additional spending, including $549 million in direct medical costs. Projection to 10 years of incident cohorts would lead to approximately 23,000 recurrences, 16,000 deaths, 77,000 lost years of life and $6 billion in direct medical costs. Conclusions: Patients with HER2+ ESBC who do not achieve pCR after neoadjuvant therapy are at ongoing risk of recurrence despite the effectiveness of treatment with T-DM1. There is substantial clinical and economic value in further reducing the recurrence risk among this population. Findings for 2021 Cohort Projected over 10 YearsWith recurrenceNo recurrenceDifferenceLocal/regional recurrences4450445Distant recurrence1,83401,834Breast cancer deaths1,55901,559Non-breast cancer deaths416457-41Direct costs$573M$24M$549MIndirect costs$86M$3.6M$82MLife years90,24997,993-7,744Costs$659M$27M$632M Citation Format: David L Veenstra, Nathaniel Hendrix, Chantal M Dolan, Kathryn Fisher, Deepa Lalla, Nina Hill, Beverly Moy. Population effectiveness model of the consequences of recurrence after trastuzumab emtansine (T-DM1) treatment among U.S. patients with high-risk HER2+ early-stage breast cancer (ESBC) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-16-01.