The Optimal Radioimmunotherapy Combinations for Advanced TNBC

Inclusion criteria

• Inoperable locally advanced/metastatic triple-negative breast cancer (defined as ER and PR \<1%; and HER2 negative as IHC 0 or IHC 1+, or IHC 2+ but negative upon fluorescence in situ hybridization (FISH) testing). Patients with ER/PR ≤10% and deemed unsuitable for endocrine therapy by the investigator are also eligible.
• No prior chemotherapy for advanced/metastatic disease.
• ECOG PS score of 0 or 1.
• Presence of 1 to 5 tumor lesions suitable for radiotherapy (individual lesion size between 0.5 and 5 cm, not limited to 1 to 2 organs).
• At least one measurable lesion outside the radiation field that can be evaluated.
• Suitable to receive one of the chemotherapy regimens chosen by the investigator: nab-paclitaxel or gemcitabine + carboplatin.
• Patients with brain metastases are allowed if they do not require local therapy at enrollment or if the metastatic lesion is treated with the assigned radiotherapy regimen.
• Patients who have previously received PD-1/PD-L1 therapy for early-stage disease are allowed to enroll.
• Able to provide tumor tissue sections or agree to tumor biopsy during the screening period.
• Adequate organ and bone marrow function, with specific requirements:
• Hematology: Neutrophil count (ANC) ≥1.5×10\^9/L; Platelet count (PLT) ≥90×10\^9/L; Hemoglobin (Hb) ≥90 g/L; No blood product transfusion (including red blood cell and platelet products, etc.) or growth factor (including colony-stimulating factors, interleukins, and erythropoietin, etc.) support treatment within 2 weeks prior to examination.
• Liver function: Serum total bilirubin (TBIL) ≤1.5×upper limit of normal (ULN); Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) ≤2.5×ULN (for patients with liver metastases: ALT and AST ≤5×ULN).
• Renal function: Serum creatinine (Cr) ≤1.5×ULN or creatinine clearance \>60 mL/min.

Exclusion criteria

• Received platinum-containing regimens during the adjuvant/neoadjuvant therapy phase, and the interval from the last treatment to recurrence/metastasis is less than 6 months.
• Have received radiotherapy within 12 weeks prior to enrollment, unless the radiotherapy was for adjuvant purposes and there are lesions outside the previously irradiated field.
• Extensive tumor metastasis with surrounding normal tissues that cannot tolerate radiotherapy damage.
• Significant third-space fluid retention (e.g., ascites, pleural effusion, pericardial effusion).
• Require long-term systemic corticosteroid treatment.
• Have active autoimmune diseases.
• Have concurrent severe infections.
• Other patients deemed unsuitable for enrollment by the investigator.