Neoadjuvant SBRT Followed by Nab-Paclitaxel Combined With Toripalimab in HR+/HER2- Breast Cancer

The prescribed dose of radiation is 24 Gy delivered in 3 fractions (8 Gy/fraction) using SBRT technique. Subjects received SBRT for the primary breast cancer lesion at 8Gy/Fraction each time for 3 consecutive days, 1 week before the start of systemic therapy. The first day of radiation is C1D1.

Toripalimab will be administered at a fixed dose of 240 mg via intravenous infusion every 3 weeks (q3w). The first dose is given on Cycle 2 Day 1 (C2D1), followed by dosing on the first day of each subsequent cycle for a total of 4 cycles. (Toripalimab×4 240mg D1 q3w)

Combined with Toripalimab, Nab-paclitaxel will be dosed at 125 mg/m² based on body surface area, administered by intravenous infusion weekly (Days 1, 8, 15 of each 21-day cycle) for 4 cycles.(T×4, Nab-Paclitaxel 125mg/m2，D1、D8、D15 q3w).

Surgery will be performed 2-6 weeks after completion of neoadjuvant therapy. The surgical approach will be determined by the investigator based on disease status and patient preference.

The anthracycline may be either Epirubicin (body surface area-adjusted 50 mg/m²) or Liposomal Doxorubicin (body surface area-adjusted 30 mg/m²) combined with Cyclophosphamide (body surface area-adjusted 600 mg/m²). Both drugs were administered intravenously every 3 weeks, and then the first day of each course was administered for 4 cycles. (EC×4, Epirubicin 50 mg/m² or Liposomal Doxorubicin 30 mg/m², comined with Cyclophosphamide 600 mg/m², D1, q3w)

Conventional radiotherapy will be delivered to the breast/chest wall and regional lymph nodes (investigator-selected technique), with explicit prohibition of tumor bed boost irradiation.

Investigator-selected adjuvant endocrine therapy will be deterimend according to applicable guidelines, considering menopausal status, recurrence risk, treatment history, comorbidities as well as patient preference.