Sarcomatoid malignant pleural mesothelioma (SMPM) is a rare disease with no effective treatment and a poor prognosis. Here, we encountered a case of programmed death ligand 1 (PD-L1)-negative SMPM with a favorable and sustained response to second-line nivolumab. Nivolumab is a human mAb to the PD-1 receptor that inhibits the interaction between PD-1 and its ligands, PD-L1 and PD-L2. Nivolumab showed promising results in several phase II trials on pretreated malignant pleural mesothelioma (MPM) patients. The patient was an 82-year-old male. He had a complaint of dyspnea on exertion and visited a local doctor. Left pleural effusion was noted, and the patient was referred to our hospital. He was diagnosed with SMPM by pleural biopsy. The patient received four cycles of chemotherapy (carboplatin and pemetrexed); however, his condition progressed. Nivolumab was selected as the second-line treatment. CT imaging showed a clear improvement in pleural thickening, and thus, the administration of nivolumab was continued. PD-L1 IHC tests (SP142 and 22C3 clones) have been negative. SMPM does not respond well to systemic chemotherapy. In epithelioid MPM and SMPM, anti-tumor immune responses by hosts differed. SMPM patients may be better candidates for immune checkpoint inhibitors (ICIs). Nivolumab needs to be considered for patients with SMPM. Further studies are needed to identify predictive biomarkers of ICIs for SMPM.
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