Abstract PS3-11-11: A comparative study of trastuzumab and pertuzumab combination subcutaneous and intravenous infusion in patients with HER2-positive breast cancer: a retrospective and prospective combined study of time efficiency, cost-effectiveness, quality of life, and socioeconomic impact

Abstract Background: Intravenous infusion of trastuzumab plus pertuzumab takes 60-150 minutes per dose, which restricts both patients and chemotherapy room beds for long periods of time. A subcutaneous (SC) formulation was approved for insurance coverage in Japan in 2023, but real-world evidence on time efficiency and cost-effectiveness is lacking. Methods: This is a single-center retrospective and prospective combined study conducted at our institution from March 1, 2024, to June 30, 2025, targeting HER2-positive breast cancer patients who received trastuzumab plus pertuzumab IV or SC administration. A total of 302 IV administrations and 269 SC administrations were extracted from electronic health records, and chemotherapy room-stay times were compared by regimen. A prospective questionnaire was administered to 54 patients in the IV group and 41 patients in the SC group (including 21 patients with experience in both groups), along with 18 questions similar to those asked of healthcare providers. The primary outcome measures were chemotherapy room-stay time and total costs associated with chemotherapy. Secondary outcome measures included patient treatment satisfaction, psychological burden, and convenience, as well as healthcare providers' perceptions of workload, efficiency, safety, and satisfaction. Results: In the case of trastuzumab plus pertuzumab monotherapy, the median chemotherapy room-stay time was 133.5 minutes (95% CI 112.4-167.3) in the IV group and 44.0 minutes (95% CI 31.4-59.3) in the SC group. When combined with docetaxel, the median was 213.0 minutes (95% CI 181.6-256.8) in the IV group, SC group was 167.5 minutes (95% CI 134.6-236.6). When combined with eribulin, the median was 198.0 minutes (95% CI 160.8-266.2) in the IV group and 107.0 minutes (95% CI 83.6-164.7) in the SC group. Regarding costs, when calculating the costs of medical supplies and labor expenses for the perioperative one-year administration of trastuzumab plus pertuzumab monotherapy, the IV group was 88,690 yen, and the SC group was 2,733 yen, with the IV group being higher. On the other hand, patient out-of-pocket expenses remained unchanged due to the high-cost medical care system. Furthermore, according to a questionnaire survey, both patients and healthcare professionals reported higher satisfaction with the SC group, and patients were more likely to choose the SC group than healthcare professionals. Discussion: In clinical practice, SC formulations significantly reduced the length of stay in the outpatient chemotherapy room compared to IV formulations and demonstrated high satisfaction among both patients and healthcare professionals. The reduction in staying time was consistent not only with trastuzumab plus pertuzumab monotherapy but also with chemotherapy combination regimens. Costs for medical supplies and labor were lower in the SC group, suggesting potential for cost savings. However, patient out-of-pocket expenses remained unchanged due to the high-cost medical care system. These results provide real-world evidence supporting the pharmacokinetic non-inferiority of the FeDeriCa trial and the high patient preference demonstrated in the PHranceSCa trial. However, limitations include the single-center, short-term observation and the fact that cost analysis was limited to cases without complications. A comprehensive evaluation through multi-center, long-term observations is necessary. Conclusion: The SC formulation of trastuzumab and pertuzumab may be a useful treatment option for HER2-positive breast cancer, improving time efficiency and patient satisfaction. Citation Format: J. Mase, A. Ogiso, H. Kinomura, K. Ishihara, H. Ohno, S. Mano, Y. Nagao. A comparative study of trastuzumab and pertuzumab combination subcutaneous and intravenous infusion in patients with HER2-positive breast cancer: a retrospective and prospective combined study of time efficiency, cost-effectiveness, quality of life, and socioeconomic impact [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 PS3-11-11.