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

Aim: To report of severe chronic oral mucositis (OM) in two pembrolizumab-treated cancer patients. Materials & methods: 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. Results: 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. Conclusion: 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.