Cisplatin plus pemetrexed therapy and subsequent immune checkpoint inhibitor administration for malignant peritoneal mesothelioma without pleural lesions Case report

Rationale: Malignant peritoneal mesothelioma is a rare tumor with a poor prognosis and has no recommended therapy after first-line pemetrexed and platinum-based chemotherapy. Moreover, effects of immune checkpoint inhibitors on peritoneal mesothelioma remains to be elucidated. We herein report the case of a 75-year-old man with peritoneal mesothelioma treated with cisplatin plus pemetrexed and subsequent nivolumab. Patient concerns: A 75-year-old man was referred to our hospital due to lower abdominal pain. Diagnosis: Positron emission tomography-computed tomography (CT) showed the accumulation of fluorodeoxyglucose in an intraperitoneal mass. A histological examination of a laparoscopic biopsy specimen revealed malignant peritoneal mesothelioma. Interventions: After 4 cycles of cisplatin plus pemetrexed and 13 subsequent cycles of pemetrexed maintenance therapy showed beneficial responses until CT revealed liver metastasis. Nivolumab was then administered as the second-line therapy. Outcomes: After 3 cycles of biweekly nivolumab administration, he developed severe abdominal distention. CT revealed an intraperitoneal mass growing much more rapidly than ever, indicating hyperprogressive disease after nivolumab treatment. He ultimately died 51 days after the initial nivolumab administration. Lessons: To our knowledge, this is the first report of hyperprogressive disease in a case of peritoneal mesothelioma after nivolumab treatment. While immune checkpoint inhibitors may be promising therapeutic strategies for treating malignant peritoneal mesothelioma, careful monitoring must be practiced with their application.