Rapid and clinically significant response to masitinib in the treatment of mucosal primary esophageal melanoma with somatic KIT exon 11 mutation involving brain metastases: A case report.

BACKGROUND: Malignant melanoma in the gastrointestinal tract may be primary or metastatic. Mucosal melanoma is a quite rare and aggressive disease, growing hidden and diagnosed with a certain delay which makes treatment difficult. CASE REPORT: The authors present the first patient with c-kit exon 11 mutated primary esophageal melanoma treated with oral tyrosine kinase inhibitor masitinib. A 55-year-old-man presented with esophageal melanoma metastising into visceral organs and to the brain. The patient showed objective and clinical significant therapeutic response to masitinib. After initiation of masitinib, dysphagia and odynophagia disappeared within 1 week. Following 1 month of treatment, computed tomography showed a regression in the number and size of brain metastatic lesions and regression in visceral lesions. This therapeutic response, despite the aggressive disease on treatment initiation, effectively enabled the patient to have 6 months of quality life. CONCLUSION: This report corroborates the plausibility of treating advanced melanoma carrying a mutation of KIT with masitinib. It also raises the question of masitinib treatment beyond progression. Additionally, the observed masitinib treatment effect on the brain suggests accumulation of therapeutically relevant concentration of masitinib in the central nervous system. This observation has possible ramifications for treatment of intracranial neoplasms.