Abstract
Background. An abscopal effect refers to a rare phenomenon in radiotherapy characterized by tumor regression outside the irradiated volume. Abscopal effects in malignant pleural mesothelioma are extremely rare. Case. A 75-year-old man was treated with palliative radiotherapy for the purpose of pain relief after the postoperative recurrence of epithelial malignant pleural mesothelioma. Two months later, his pain was improved; however, CT showed an exacerbation of the non-irradiated lesions. His serum cytokeratin fragment (CYFRA 21-1) level (36.0 ng/ml) was elevated. Six months later, his serum CYFRA 21-1 level decreased to 5.5 ng/ml, and a marked reduction of the lesions outside of the irradiation field was observed. After palliative or whole-brain irradiation for subsequent recurrence and the administration of nivolumab, a PD-1 inhibitor, CT revealed partial tumor shrinkage and his serum CYFRA 21-1 level decreased 1 month later. Conclusion. It was suggested that the effect of an immune checkpoint inhibitor could be expected after radiotherapy in a patient with malignant pleural mesothelioma, or that the appearance of an abscopal effect could be a predictor of the effect of immune checkpoint inhibitor treatment.
