Mesothelioma is a rare neoplasm with a minority of cases originating from the peritoneum. Patients are generally treated with a combination of cytoreductive surgery, hyperthermic intraperitoneal chemotherapy, and various systemic therapies. In recent years, expression of programmed death ligand 1 (PD-L1) has been investigated in mesothelioma with implications for targeted therapy. In this case report, we present a patient with solitary isolated peritoneal mesothelioma of the right flank with abdominal and chest wall involvement and high PD-L1 positivity. The patient demonstrated a remarkable metabolic response to neoadjuvant immunotherapy using nivolumab and ipilimumab, which was followed by a successful surgical resection. Pathological evaluation revealed a complete pathological response, highlighting the effectiveness of the treatment strategy.
Keywords: PD-L1; Peritoneal mesothelioma; immune checkpoint inhibitors; ipilimumab; neoadjuvant immunotherapy; nivolumab; solitary peritoneal mass.
Peritoneal mesothelioma is a rare and aggressive cancer that forms in the lining of the abdomen. Most patients receive surgery and chemotherapy, but outcomes are often poor, and there is no widely agreed-upon best treatment. In this report, we describe the case of a 51-year-old man who had a single, large tumor on the right side of his abdomen. After testing, the tumor was found to express high levels of a protein called PD-L1, which can make cancers more responsive to certain immunotherapies.The patient received a combination of two immunotherapy drugs – nivolumab and ipilimumab – before surgery. This treatment led to a dramatic reduction in the tumor’s activity and size. Surgery was then performed to remove the tumor along with part of the liver and two ribs. After surgery, testing showed that no live cancer cells remained. The patient continued immunotherapy and remained free of cancer 3 years later.This case highlights a promising treatment approach for selected patients with peritoneal mesothelioma using immunotherapy before surgery. More research is needed, but this strategy could offer hope to patients with similar tumors, especially when the cancer expresses PD-L1.