Malignant peritoneal mesothelioma (MPM) is an uncommon but aggressive neoplasm and has an association with asbestos exposure. MPM has low survival rates of approximately one year even after palliative surgery and/or systemic chemotherapy. Recent advances in treatment strategies focusing on cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) have resulted in improved median survival of 53 months and a 5-year survival of nearly 50%. However, recurrence rates are

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... Current systemic chemotherapy in the adjuvant setting is of limited efficacy, while immunotherapy with dendritic cell based immunotherapy (DCBI) has yielded promising results in murine models with peritoneal mesothelioma and in patients with pleural mesothelioma. The goal of the study is to assess the feasibility of administering DCBI after CRS-HIPEC in patients with MPM. Secondary objective of this study is to assess safety in patients with peritoneal mesothelioma who are treated with DCBI, which has already been proven in patients with pleural mesothelioma. Another secondary endpoint of this study is the determination of an immunological response against the tumor as result of the adjuvant therapy. Methods We will conduct an open-label single-center phase II study. The study population will consist of adult patients with a histologically confirmed diagnosis of MPM. 4 to 6 weeks before CRS-HIPEC a leukapheresis will be performed of which the monocytes will be used for differentiation to dendritic cells (DCs) using specific cytokines. These DCs will be pulsed with PheraLys, a tumor cell lysate derived from 5 well-characterized cell lines from patients with malignant mesothelioma. The tumor lysate-pulsed autologous DCs (MesoPher) are re-injected 8-10 weeks after surgery, 3 times every two weeks. After the third injection with MesoPher, revaccinations to boost the immune system are given after 3 and 6 months. Results Start of enrolment is planned for March 2018, and we expect to have enrolled al patients by March 2020. Results are expected in September 2020. Conclusion The MESOPEC study will determine if administering DBCI in patients with MPM after CRS-HIPEC is feasible and safe. This study could be the first step for new treatment strategies that will show prolonged survival with limited adverse effects in patients with MPM.