Biphasic malignant pleural mesothelioma successfully treated with multidisciplinary therapy: efficacy of postoperative combination therapy with nivolumab and ipilimumab

Malignant pleural mesothelioma (MPM) is a relatively rare disease but has shown an increasing trend in Japan in recent years as an asbestos-related disease. MPM generally has a poor prognosis, and its treatment primarily relies on multidisciplinary therapy. Surgical intervention is the mainstay for the resectable cases, while drug therapy is primarily used for unresectable cases or postoperative recurrence. In Japan, only four drugs are approved for the treatment of MPM: cisplatin, pemetrexed, nivolumab, and ipilimumab. While chemotherapy with cisplatin and pemetrexed has been the standard treatment, the recent addition of immune checkpoint inhibitors nivolumab and ipilimumab to the approved drugs has expanded the treatment options. We present a case of 71-year-old man with a history of asbestos exposure who presented with left thoracic back pain for two months and visited our internal medicine department. Chest X-ray and CT findings suggested MPM, and he was referred to our department. Imaging revealed multiple soft tissue masses of varying sizes extensively involving the left dorsal pleura and suspected invasion into a part of the left lung. There was a little pleural effusion. Preoperative diagnosis was cT3N0M0, cStage IB MPM, and macroscopic complete resection was deemed possible. We performed pleurectomy/decortication (P/D). Histopathological examination, including HE staining and immunohistochemical staining of the resected specimen, confirmed a diagnosis of biphasic MPM. As a part of the multidisciplinary therapy, we added postoperative combination therapy with nivolumab and ipilimumab. The patient has been followed for one year postoperatively without recurrence and remains in good condition. The combination therapy with nivolumab and ipilimumab is reported to extend overall survival compared to cisplatin plus pemetrexed, with higher efficacy in non-epithelial (sarcomatoid, biphasic) types than in epithelioid types.