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

This study is a prospective, single-center, open-label, real-world observational clinical study that plans to enroll 10 to 15 patients with advanced (Stage IV) breast cancer who have failed multiple lines of prior therapy (aged 18-75 years, with ECOG performance status 0-2, and with measurable and injectable tumor lesions). It aims to preliminarily explore the antitumor activity, safety, and impact on the tumor immune microenvironment of intratumoral H101 oncolytic virus injection combined with immune checkpoint inhibitors (ICIs) in a real-world clinical setting. The study does not interfere with routine clinical decisions; the specific combination regimen (H101 intratumoral injection plus an anti-PD-1 or anti-CTLA-4 antibody) is determined by the attending physician based on the patient's condition, prior treatments, and multidisciplinary team recommendations. However, to ensure consistent observation, a standardized treatment framework is established: each cycle lasts 2-3 weeks; on day 1 of each cycle, H101 is injected intratumorally (dose stratified by lesion size according to the package insert, e.g., 5×10¹¹ VP per session with divided injections), and intravenous ICI infusion is started 7±2 days after the first injection, with a planned total of 4 cycles. To analyze biological changes before and after treatment, the study includes a systematic sampling plan: at baseline and after completion of 4 cycles, we attempt to re-biopsy the same accessible lesion whenever possible and also collect peripheral blood. These paired samples will be used for single-cell RNA sequencing and immune microenvironment analysis, focusing on changes in the composition, functional status, and differentially expressed genes of key immune cell subsets (T cells, NK cells, dendritic cells, macrophages), and correlating these changes with clinical efficacy indicators. For efficacy and safety evaluation, the primary endpoints include the incidence and severity of treatment-related adverse events (assessed by CTCAE v5.0), objective response rate and local lesion control rate (by RECIST 1.1), as well as feasibility and tolerability measured by the 4-cycle completion rate and the rate of treatment discontinuation due to toxicity. Secondary endpoints include disease control rate, progression-free survival (estimated using the Kaplan-Meier method for median survival time), and the paired dynamic changes in the above immune microenvironment markers from baseline to post-treatment. For follow-up and data collection, the first radiographic efficacy evaluation is performed 6-8 weeks after treatment completion, and then every 3 months thereafter until disease progression, loss to follow-up, or 1 year. In consideration of real-world operational practicality, if the injected lesion markedly shrinks, becomes necrotic, or cannot be safely re-biopsied after treatment, only peripheral blood samples may be collected without being considered a protocol violation. Comprehensive follow-up management, data confidentiality, and missing data handling measures are also in place to maximize the scientific rigor of the study and safeguard the rights and safety of participants.