Malignant melanoma with in-transit metastases refractory to programmed cell death-1 inhibitor successfully treated with local interferon-β injections: A case report

In-transit metastases (ITMs) in patients with malignant melanoma (MM) are associated with poor prognosis and a worse disease burden compared with MM without ITMs. A substantial population of patients with ITMs show no or only poor responses to newly developed therapies, such as immune checkpoint inhibitors or molecular-targeted agents. It is difficult to control the exudate and bleeding from ITMs when these medications are ineffective. In Japan, local injection of interferon-β (IFN-β) has been licensed for years as adjuvant therapy for MM. However, the evidence for IFN-β effectiveness for ITMs remains low. The present report describes a case of MM with multiple ITMs that did not respond to a programmed cell death-1 inhibitor and local injections of IFN-β at 3 million IU/day for 5 days/4 weeks but remitted upon increasing the amount of IFN-β injections to 10 consecutive days/4 weeks. Local IFN-β therapy could be an option for improving the quality of life of patients.