Nivolumab-induced immune thrombocytopenia in a patient with malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and highly aggressive tumor. Nivolumab showed durable antitumor effect in patients with recurrent MPM and was approved for those patients in Japan in 2018. Immune related adverse event (irAE) is occurred in various organs and is suggestive to be related to better outcome of nivolumab. Frequency of hematological irAE is low and there are few reports about hematological irAE and association between irAE and outcome of nivolumab in patients with MPM. We present a case of recurrent MPM who responded to nivolumab treatment and experienced nivolumab-induced immune thrombocytopenia (ITP). Although high dose dexamethasone was administered and platelet count increased transiently, re-administration of dexamethasone was required to maintain normal count of platelet. The careful and intensive management of ITP treatment is necessary in cases who show no response or relapse to initial glucocorticoids treatment. This is the first report about nivolumab-induced ITP and association with response to nivolumab in MPM.