Unexpected Anti-tumor Effect of Selective Internal Radiation Therapy and Radiofrequency Ablation Followed by Immune Checkpoint Inhibitors for Hepatocellular Carcinoma

Introduction: Hepatocellular carcinoma (HCC) has become an increasingly serious health problem worldwide. Combining immune checkpoint inhibitors (ICIs) for HCC with local treatments can produce synergistic effects. Although the abscopal effect was noted in 1953, most studies on this phenomenon have been conducted in the context of external beam radiotherapy (EBRT). The incidence of the abscopal effect induced by selective internal radiation therapy (SIRT) alone is lower. This research reports a case of a patient with multifocal HCC who received SIRT plus radiofrequency ablation (RFA) followed by ICI therapy. During the subsequent course of ICI therapy, an anti-tumor effect was detected in the left hepatic lobe, far from the site targeted by the local treatments. Case Presentation: The abscopal effect has recently attracted widespread attention because ICIs can enhance this phenomenon. However, little is known about the relationship between inducing the abscopal effect and local treatment against HCC. A 76-year-old male patient presented with multifocal HCC. During hepatic angiography, MRI showed multiple HCCs in both lobes of the liver. Selective internal radiation therapy was performed on a tumor with a diameter of approximately 80 millimeters in the right lobe. A month later, RFA was conducted on another tumor in the right lobe, approximately 30 mm in diameter, and ICI therapy was administered on the second day post-RFA. Hepatic arterial phase imaging of contrast-enhanced magnetic resonance performed 10 months after SIRT showed the disappearance of the tumor in the left liver lobe. Conclusions: This case highlights that the combination of multiple local treatment methods with ICI therapy can enhance the anti-tumor immune response and benefit patients with multifocal