A Real-World Observational Study of Intratumoral H101 Oncolytic Adenovirus Combined With Immune Checkpoint Inhibitors for Advanced Metastatic Breast Cancer

Inclusion Criteria: * Age 18 to 75 years, both genders; * Pathologically confirmed breast cancer (Stage IV)； * Disease progression after at least one line of standard systemic therapy； * ECOG performance status 0-2； * Intolerant to or refusal of standard chemotherapy； * At least one radiologically measurable lesion per RECIST 1.1 criteria； * At least one lesion amenable to puncture/injection (i.e., accessible for intratumoral injection)； * Estimated life expectancy ≥3 months； * Adequate major organ function as defined by the following laboratory values:Absolute neutrophil count (ANC) ≥1.5×10⁹/L,Platelet count (PLT) ≥100×10⁹/L,Hemoglobin (Hb) ≥90 g/L,Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) ≤2.5× upper limit of normal (ULN),Serum creatinine (Cr) ≤1.5× ULN； * Signed informed consent form； * Agreement to provide tumor tissue samples and peripheral blood samples before and after treatment for research purposes.。 Exclusion Criteria: * Known allergy to H101 formulation, PD-1 inhibitors, or any of their excipients ; * Lymphocyte count \<0.5×10⁹/L; * Severe infection, active infection (particularly HBV, HCV, HIV), or severely immunocompromised status; * Presence of lesions that cannot be safely punctured/injected; * Prior treatment with PD-1/PD-L1 inhibitors with grade ≥3 immune-related adverse events that have not resolved; * Concurrent active malignancy other than breast cancer (except for those cured for \>5 years with no evidence of recurrence); * Uncontrolled brain metastases; * Pregnant or breastfeeding wome; * Psychiatric disorders, cognitive impairment, or poor compliance that may interfere with study participation and completion; * Severe cardiac, hepatic, or renal failure; * Long-term immunosuppressive therapy; * Uncontrolled active autoimmune disease.