Abstract PS3-07-04: Neoadjuvant chemotherapy combined with Toripalimab for HR+/HER2- breast cancer : a prospective, single-arm, multi-center clinical study (NEOTORCH-BREAST01)

Abstract Background: Hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer (BC) exhibits low pathologic complete response (pCR) to neoadjuvant therapy, urgently requiring more effective alternatives. The phase III trials KEYNOTE-756 and CheckMate-7FL demonstrate the potential of neoadjuvant immunotherapy combined with chemotherapy in HR+/HER2- breast cancer. Here we aim to evaluate the efficacy and safety of toripalimab combined with neoadjuvant chemotherapy plus adjuvant toripalimab in HR+/HER2- BC, with the goal of providing more treatment options and potential theoretical support for precision therapy in breast cancer Method: This is a prospective, single-arm, phase II clinical trial. Eligible patients are women aged 18-75 years, treatment-naïve, with histologically confirmed invasive breast cancer at stage cT1c-3/N0-3M0 and HR+/HER2- status. Following enrollment, patients will receive neoadjuvant treatment consisting of toripalimab (240 mg, Q3W) combined with epirubicin (100 mg/m2) or liposomal doxorubicin (35 mg/m2), each administered with cyclophosphamide (600 mg/m2) for 4 cycles, followed by nab-paclitaxel (260 mg/m2, Q3W) for 4 cycles.Surgical treatment will be performed 2-4 weeks after completion of neoadjuvant therapy. After definitive surgery, patients will receive adjuvant treatment with toripalimab (240 mg, Q3W) for 8 administrations, combined with endocrine therapy (ET).The primary endpoints are pathologic complete response (pCR) and residual cancer burden (RCB) 0-1. Secondary endpoints include safety, event-free survival (EFS), progression-free survival (PFS), and disease-free survival (DFS). Results: As of July 6, 2025, 37 patients had been enrolled in the study. The median age was 52 years. Of all patients, 40.5% (15/37) were premenopausal, 73% (27/37) had node-positive disease, 81.1% (30/37) had clinical stage II, 18.9% (7/37) had clinical stage III. 73.0% (27/37) had ER expression≥50%, 37.8% (14/37) had PR expression≥50%, and 89.2% (33/37) had Ki67 expression≥15%, 37) .Among the 29 patients completed neoadjuvant therapy and underwent surgery, the current pCR was 44.9% (13/29), and the postoperative RCB0/1 was 65.5% (19/29). Subgroup analyses among the 29 patients who and underwent surgery further showed: 31.3% (5/16) patients in ER≥90 subgroup reach pCR. For CPS (Combined Positive Score) within this operated cohort, 1 patient with CPS 1 did not achieve pCR but reached RCB0/1; among 7 patients with 1 ≤ CPS 10, none achieved pCR and only 1 reached RCB0/1; in 15 patients with CPS ≥10, 11 achieved pCR and all 15 attained RCB0/1. For TILs (Tumor-Infiltrating Lymphocytes) in the same operated group, among 11 patients with TILs 10, 2 patients achieved pCR and 4 patients reached RCB0/1; in 8 patients with 10 ≤ TILs 30, 3 achieved pCR and 5 reached RCB0/1; in 6 patients with TILs ≥30, 5 achieved pCR and all 6 attained RCB0/1. 65.5% (19/29) of patients experienced at least one treatment-related adverse event (TRAE). Grade 3 or higher TRAEs occurred in 37.9% (11/37) of patients. Conclusion: Preliminary results indicate that toripalimab-based neoadjuvant chemotherapy achieves favorable efficacy signals in HR+/HER2- breast cancer, with a safety profile consistent with prior immunotherapy studies. These data support the potential of this regimen to expand therapeutic options for patients with HR+/HER2- BC, and long-term follow-up will further clarify its impact on survival endpoints including EFS, PFS, and DFS.Clinical trial information: NCT06611813. Citation Format: Y. Chen, G. Zhong, L. Chen, J. Ma, H. Cui, B. Wei, W. Shao, Y. Wang, P. Fu, Z. Dai. Neoadjuvant chemotherapy combined with Toripalimab for HR+/HER2- breast cancer : a prospective, single-arm, multi-center clinical study (NEOTORCH-BREAST01) 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 PS3-07-04.