Procedure considerations for image-guided intratumoral immunotherapy: A retrospective study of 357 cases.

e14644 Background: Tumor in situ immunotherapy functions as an "in situ vaccine," eliciting a systemic immune response. However, detailed reports on the operational specifics are scarce. This study presents the largest cohort of tumor in situ immunotherapy operations to date, which aims to refine the operational details of tumor in situ immunotherapy, and assess its feasibility and safety in clinical practice. Methods: This study retrospectively analyzed 357 tumor in situ immunotherapy injections performed at The Comprehensive Cancer Centre of Nanjing Drum Tower Hospital between May 2019 and December 2024.Standard operating procedures (SOP) were established, with oncologists assessing risk prior to the procedure. After informed consent, drug volumes and guidance methods were selected: ultrasound for deeper lesions (e.g., liver) and CT for superficial ones (e.g., lungs, chest wall, limbs). Following routine disinfection and 2% lidocaine anesthesia, a coaxial biopsy needle was used, with injection depth based on tumor size. Tumors >5 cm received four depths; tumors <5 cm, three. For round tumors, a 45°-angled multi-point injection was performed, while for ellipsoid tumors, 2-3 puncture points were selected. Post-procedure, adverse reactions were documented and graded according to CTCAE V5.0. Results: 357 tumor-in-situ immunotherapy injections included liver cancer, gastric cancer, renal cancer, breast cancer, endometrial cancer, soft tissue sarcoma, etc. The most common injection sites included the liver (26.4%), abdominal cavity (24.7%), limbs (17.6%), lungs (15.3%), pelvis (8.2%). Injections were guided by CT in 52.7% and ultrasound in 47.3%. The primary injection-related adverse reactions were injection site pain (7.0%), bleeding (1.7%), injection site reactions (0.6%), and skin ulcers (0.3%). Notably, 63 procedures were performed in the lungs, chest wall, and mediastinum, where pneumothorax was the most common adverse reaction (4.8%). Importantly, no patients experienced serious injection-related adverse reactions such as skin induration, intraoperative nerve injury, or chest wall necrosis and no Grade ≥3 adverse reactions were observed. Conclusions: This study suggested that intratumoral immunotherapy is a feasible approach for treating tumors, including those in the liver, abdominal cavity, limbs, lungs, etc. This approach represents a promising direction for the advancement of immunotherapy and offers new treatment options for patients with metastatic solid tumors. Adverse reactions. Tumor Location Adverse reactions Grade 1 Grade 2 Grade≥3 All tumor location(N=357, Visceral lesions=95 (26.4%) Injection site pain 22 (6.2%) 3 (0.8%) 0 Hemorrhage 6 (1.7%) 0 0 Injection site reactions 2 (0.6%) 0 0 Skin ulcer 1 (0.3%) 0 0 Only lung ,chest wall, mediastinum (N=63) Pneumothorax 2 (3.2%) 1 (1.6%) 0 Pleural infection 0 0 0 Necrosis of the chest wall 0 0 0