A Case of Oral Mucosal Malignant Melanoma Treated with an Immune Checkpoint Inhibitor and Carbon-Ion Radiotherapy

Abstract

Mucosal malignant melanoma is a fast-growing and difficult-to-control disease. New treatments, for example, carbon-ion radiotherapy and immune checkpoint inhibitors have been developed and appropriate treatment strategies including these treatments may need to be considered.

Herein, we report a case of oral mucosal melanoma with multiple cervical lymph node metastases treated with an immune checkpoint inhibitor and carbon ion radiotherapy.

The patient was a 50-year-old woman diagnosed as having malignant melanoma of the mandibular gingiva with left cervical lymph node metastasis. She received four courses of nivolumab therapy before carbon-ion radiotherapy. The metastatic lymph node enlarged until immediately after the second course of nivolumab, however, thereafter, a tendency towards shrinkage was observed. However, the lymphadenopathy persisted even after carbon-ion radiotherapy, therefore, the patient received two courses of combined nivolumab and ipilimumab therapy. However, the treatment had to be discontinued before the third course because of the development of Grade 4 liver dysfunction. The liver damage improved with steroid pulse therapy and the metastatic lymph nodes continued to shrink.

In this report, we also review the data of 23 cases of mucosal malignant melanoma who received carbon-ion radiotherapy from 2017 to 2020 at the Kanagawa Cancer Center and discuss their outcomes. Of the 23, 19 cases (87%) developed metastasis after carbon-ion radiotherapy, including distant metastasis in 12 cases (60%). For cases of advanced mucosal malignant melanoma, we believe that an effective and safe combination of topical and systemic treatment is needed.