The synergy of RT plus ad-LIGHT immunotherapy eradicates distant metastases. 4T1 tumor: Balb/c mice were subcutaneously injected with 10⁵ cells on the lower back. Mice received local RT (12 Gy) on days 14 and 15 and intratumoral injection with ad-control (2 × 10¹⁰ virus particles [vp]) or ad-LIGHT (2 × 10¹⁰ vp) on days 15 and 16 (n = 24-41 pooled from 5 experiments). B16-CCR7 tumor: C57BL/6 mice were subcutaneously injected with 10⁵ cells on the lower back. Mice received local RT (12 Gy) on days 14 and 15 and intratumoral injection with ad-control (2 × 10¹⁰ vp) or ad-LIGHT (2 × 10¹⁰ vp) on days 15, 16, and 17 (n = 6-9 pooled from 2 experiments). On day 25 after tumor injection, tumors were surgically removed. Mice were killed on day 35 for tumor colonogenic assay (n = 4 or 5 per group). No colonies were detected in combination group in both types of tumor. Similar experiments were repeated 3 times.