Oral mucosal melanoma treated with carbon ion radiotherapy: a case report

BACKGROUND: Oral mucosal melanoma is a rare disease with a relatively poor prognosis. Carbon ion radiotherapy has been shown to be effective against radiotherapy-resistant tumors owing to its excellent dose concentration and high biological effect. CASE PRESENTATION: Our patient was a 66-year-old Japanese man with oral mucosal melanoma of his right maxillary gingiva (T4aN0M0). He received carbon ion radiotherapy at 57.6 Gy (relative biological effectiveness) in 16 fractions for 4 weeks. Concomitant chemotherapy (dacarbazine + nimustine + vincristine) was administered at the same time as carbon ion radiotherapy initiation. Two courses of adjuvant chemotherapy were given after carbon ion radiotherapy. Although he experienced grade 2 acute oral mucositis, his symptoms improved within a few weeks of undergoing carbon ion radiotherapy. He was alive at the time of reporting, 35 months after treatment, without any recurrence. Late toxicity has not been observed. CONCLUSIONS: Carbon ion radiotherapy for oral mucosal melanoma resulted in a good local effect.