Severe chronic nonlichenoid oral mucositis in pembrolizumab-treated patients: new cases and a review of the literature.

To report of severe chronic oral mucositis (OM) in two pembrolizumab-treated cancer patients. A retrospective chart review was performed. Inclusion/exclusion criteria detected patients that developed OM during pembrolizumab immunotherapy. In addition, we searched the literature for nonlichenoid OM in immunotherapy-treated cancer patients. Two male patients treated for anaplastic astrocytoma and lung adenocarcinoma were included. Extensive painful OM (grade 4) developed in both patients during the course of immunotherapy and the ulcerations remained >30 weeks (>16 weeks after stopping immunotherapy). Superficial mucocele appeared in one patient. In one patient, pain relief was achieved with photobiomodulation (low-level laser) therapy. OM induced by immunotherapy may be a major cause of suffering and eating difficulties. In most cases, the OM lasted for months even after the drug was stopped. There is a controversy regarding the beneficial effect of corticosteroids on OM in these patients.