Abscopal effect induced by conventional fractionated radiotherapy following anti-PD-1 immunotherapy in pulmonary metastatic thymic squamous cell carcinoma: a case report and literature review

The rise of immunotherapy challenges traditional RT. To enhance AE occurrence in practice, factors like radiation dose, irradiation site, timing with ICIs, ICI drug choice, patient health, disease stage, and tumor traits must be considered. This case demonstrates that CFRT can induce an AE in TSCC but also highlights the associated risk of severe lymphopenia that may limit its durability. Monitoring and mitigating lymphopenia are crucial in optimizing combined therapy outcomes. This case provides new clinical evidence for treating recurrent TSCC with combined therapy, though more research on its immunological mechanisms is needed.