Abstract PS5-04-05: Long term Breast Cancer real-world overall survival in France

Abstract Objectives Assess the Overall survival (OS) rates at 5,10 and 12 years in French women with breast cancer (BC) by BC subtype Material and methods Data were extracted from a 2% representative sample of the French National Claims Database which covers around 98% of the total French population. All French women aged ≥18 years diagnosed with BC between 2010 and 2023 were identified using markers of BC management. HER2+ and HR+ status were determined based on the reimbursement of HER2-targeted therapy and endocrine therapy, respectively. The BC subtype of patients without HER2-targeted nor endocrine therapy could not be determined because of the lack of tracking drugs. These patients constituted the “undefined” group with regard to their BC subtype and were composed of 2 main subgroups: ÏPatients treated with systemic treatment(s) (potentially composed among others of TNBC or patients with visceral crisis)ÏPatient with BC in situ diagnosis without systemic treatment A one year historical period has been used. OS was defined as the time from the BC diagnosis date, or otherwise from the date of the first evidence of BC specific treatment until death from any cause. Results A total of 12 219 incident BC cases were identified between 2010 and 2023, of which 7 878 (64,5%) were HR+/HER2- and, 1 414 (11.6%) HER2+ including 895 (7,3%) HER2+/HR+ and 519 (4,3%) HER2+/HR-. The “undefined" group (N=2 927, 24.0% of total incident BC cases) was composed of 1 188 (9.7%) patients treated with systemic treatment(s), 768 (6.3%) patients with BC in situ diagnosis without systemic treatment and 971 patients with invasive cancer diagnosis without systemic treatment (8.0 %) In the HER2+ BC subtype, the 5-years, 10-years and 12-years OS rates were 87.7% (95% CI: 85.6%, 89.4%), 80.4% (95% CI: 77.6%, 82.8%) and 74.4% (95% CI: 70.5%, 77.8%). Among HER2+, the corresponding OS rates were 90.4% (95% CI: 88.1%, 92.4%), 81.0% (95% CI: 77.3%, 84.2%) and 73.7% (95% CI: 68.3%, 78.3%) in HER2+/HR+ and 82.7% (95% CI: 78.8%, 86.0%), 79.2% (95% CI: 74.7%, 82.9%) and 75,4 (95% CI: 69.6%, 80.3%) in HER2+/HR-, showing a better survival in HER2+/HR+ at 5 years but quite similar OS rates at 12 years. In the HR+/HER2- BC subtype, the 5-years, 10-years and 12-years OS rates were 88.8% (95% CI: 88.0%, 89.5%), 77.6% (95% CI: 76.3%, 78.8%) and 73.7% (95% CI: 72.1%, 75.1%). Among the undefined group, the 5-years, 10-years and 12-years OS rates were 73.0% (95% CI: 70.1%, 75.6%), 66.7% (95% CI: 63,4.%, 69.8%) and 65.1% (95% CI: 61,5.%, 68.5%) in patients treated with systemic treatment(s), in patients treated with systemic treatment(s), which fits with the bad prognosis of TNBC and patients with visceral crisis. OS rates were 98.0% (95% CI: 96.6%, 98.8%), 93.1% (95% CI: 90.2%, 95.1%) and 91.4% (95% CI: 87.9%, 94.0%) in patients with an in situ BC diagnosis without systemic treatment, demonstrating as expected higher survival rates than other groups. Conclusion As of today, 12-year OS rates tend to be similar in HER2+ (regardless of the HR status) and HR+/HER2- groups, demonstrating an efficient BC management evolution, especially in the HER2+ group. These results also highlight a significantly higher 5-year survival for HR+ compared to HER2+. However, this difference tends to equalize at 12 years, in line with the long-term recurrence risk of HR+. Citation Format: O. Tredan, Y. Delpech, S. Bara, M. Lotz, M. Moreau, D. Stamenic, M. Le Foll-Elfounini, L. Mansi. Long term Breast Cancer real-world overall survival in France abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-04-05.