CASE REPORT article
Front. Immunol.
Sec. Cancer Immunity and Immunotherapy
This article is part of the Research TopicCancer Immunity, Modern Radiotherapy and Immunotherapy: A Journey into Cancer Treatment InnovationView all 18 articles
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
Provisionally accepted
- 1Shandong First Medical University, Jinan, China
- 2Zhangqiu People’s Hospital, Jinan, China
- 3Central Hospital Affiliated to Shandong First Medical University, Jinan, China
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Background: Radiotherapy (RT) can enhance immune control of distant metastases, known as the abscopal effect (AE), but it doesn't significantly alter the immunosuppressive tumor microenvironment (TME), resulting in low AE incidence. Combining RT with immunotherapy (especially anti-PD-1/PD-L1 agents) has increased AE occurrences, though questions remain about this approach, particularly in tumors with low immunogenicity such as thymic squamous cell carcinoma (TSCC). Case Description: A 73-year-old woman with advanced TSCC and multiple metastases experienced disease progression after two therapies. Following palliative conventional fractionated radiotherapy (CFRT) (40Gy) for thoracic metastases, her pleural lesions outside the radiation field significantly reduced, indicating an AE. Despite subsequent immunotherapy and antiangiogenic drugs, treatment efficacy was unsatisfactory due to severe lymphopenia, possibly contributing to disease progression. Conclusion: 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.
Keywords: abscopal effect, conventional fractionatedradiotherapy, Immunotherapy, optimized target volume delineation, thymic squamous cell carcinoma
Received: 27 Oct 2025; Accepted: 02 Feb 2026.
Copyright: © 2026 Cui, He, Zhang, Zhang, Gao and Liu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Ang Gao
Jie Liu
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