Proton beam therapy followed by pembrolizumab for giant ocular surface conjunctival malignant melanoma: A case report

The present study describes proton beam therapy as a clinical option to achieve local control of giant conjunctival melanoma in an aged person, instead of orbital exenteration. An 80‑year‑old woman with one‑year history of left‑eye injection and hemorrhage experienced rapid growth of the ocular surface black mass. At the initial visit, a black, elastic hard, hemorrhage‑prone, thickened mass in the size of 30x40 mm with a presumed wide stalk covered the total area of the lid fissure on the left side. Biopsy of the mass demonstrated anomalous melanin‑containing cells in fibrin and hemorrhage, which were positive for cocktail‑mix antibodies against tyrosinase, melanoma antigen recognized by T cells‑1 and human melanoma black‑45, indicative of malignant melanoma. One month after the initial visit, the patient underwent proton beam therapy at the total dose of 70.4 Gy (relative biological effectiveness) in 32 fractions (~10 min each) in one and a half months. One month after the end of proton beam therapy, 3.5 months from the initial visit, the patient was found by computed tomographic scan to have multiple metastatic lesions in bilateral lung fields. With the evidence of absent BRAF mutation, the patient underwent intravenous administration of pembrolizumab 77.2 mg every three weeks five times in total. Then, three months after proton beam therapy, ocular surface melanoma almost subsided and the clear cornea allowed visualization of the intraocular lens inside the eye. In three weeks, spontaneous corneal perforation was plugged with iris incarceration. The patient died suddenly of unknown cause 7.5 months from the initial visit. The local control of giant conjunctival melanoma was achieved by proton beam therapy, leading to patient's satisfaction and better quality of life. Proton beam therapy, followed by immune checkpoint inhibitors, would become the future standard of care for unresectable giant conjunctival melanoma.