Tumor–Immune Interactions in Pediatric Oral Rhabdomyosarcoma: A Narrative Review on Immuno-Oncology and Emerging Therapies

Abstract

Pediatric oral rhabdomyosarcoma (RMS) is a rare and aggressive cancer of the head and neck, characterized by a complex and mostly immunosuppressive tumor-immune microenvironment. Unlike adult cancers, pediatric RMS typically exhibits a "cold" immune profile, characterized by minimal T-cell infiltration, a low mutational burden, and resistance to immune checkpoint blockade. The tumor's location in the oral cavity adds difficulty to treatment because of anatomical and functional limitations. Additionally, the presence of fusion oncogenes, such as PAX3:FOXO1, hampers immunogenicity and treatment response by disrupting antigen presentation and reducing immune cell infiltration. Advances in immuno-oncology have introduced new strategies, including immune checkpoint inhibitors, chimeric antigen receptor (CAR) therapies, cancer vaccines, and oncolytic viruses. However, these approaches face specific challenges in the pediatric population due to developmental immune factors. This narrative review highlights recent findings on the immunobiology of pediatric oral RMS, focusing on tumor-immune interactions and their impact on disease progression and treatment resistance. We reviewed the cellular components of the TIME, the mechanisms of immune evasion, and the expression of immune checkpoints, including PD-L1 and B7-H3. Emerging immunotherapies, including CAR-T, CAR-NK, and CAR-CIK cell therapies; checkpoint inhibitors; oncolytic viruses; and cancer vaccines, are discussed, with an emphasis on their current limitations and potential to transform the pediatric RMS immune landscape.