First-ever Abscopal Effect after Palliative Radiotherapy and Immuno-gene Therapy for Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a highly aggressive disease, with few, if any, curative interventions. While there is growing interest in using immunotherapy and immuno-gene therapy to treat MPM, very limited data currently exist for combining these modalities with radiotherapy. Preclinical data suggest that radiotherapy may be combined with immunotherapy to produce disease regression, with abscopal effects in mice with MPM. We report the first-ever case of abscopal effect in a patient with MPM, following radiotherapy and immuno-gene therapy. The patient was a 67-year-old male with prior asbestos exposure who presented with progressive dyspnea and thoracic pain. He underwent partial right pleurectomy, pleural biopsy, and talc pleurodesis, with pathology revealing epithelioid MPM. A subsequent chest computed tomography (CT) scan and fluoro-deoxyglucose positron-emission tomography (FDG-PET) CT scan showed extensive, right-sided, fluoro-deoxyglucose (FDG) avid mass-like pleural thickening encasing the right lung, with likely mediastinal extension, nodal metastases, and vascular compression. He enrolled in a clinical trial in which he received intrapleural interferon-alpha gene therapy but needed to discontinue therapy due to supraventricular tachycardia and superior vena cava syndrome induced from tumor burden. He was emergently treated with palliative radiotherapy to 30 Gy in 10 fractions. He was then started on pemetrexed and cisplatin chemotherapy. His subsequent chest CT scan two months after radiotherapy completion showed a dramatic treatment response within, as well as outside of, the irradiated field. After completion of radiotherapy, he did experience radiation esophagitis requiring nasogastric tube placement. Herein, we highlight the feasibility and efficacy of combining immuno-gene therapy with palliative radiotherapy to produce a substantial treatment response and an abscopal effect in a patient with unresectable MPM.