Two cases of malignant melanoma with tumor regression after dacarbazine administration following immune checkpoint inhibitors

Abstract

The treatment of malignant melanoma has undergone a dramatic evolution in recent years. However, the selection of second－line treatment after initial treatment for unresectable melanomas, such as those that have not responded to immune checkpoint inhibitors (ICI), is very difficult. In fact, the tumor shrinking effect may be reactivated by interspersing radiation therapy or chemotherapy between ICI treatments. We experienced two cases of dacarbazine after nivolumab administration in which regression was seen during dacarbazine administration. The tumor in the first patient, an 83－year－old woman, continued regressing after the switch to nivolumab, and a complete response was achieved. The tumor in the other patient, a 78－year－old man, appeared to continue growing after the switch to nivolumab ; the patient finally died. The tumor burden was greater in the male versus female patient, which we believe caused the difference in efficacy. These findings suggest that dacarbazine as second－line treatment after ICI is an effective treatment choice. However, there are many unclear points about its effectiveness, and the accumulation of further cases is awaited.[Skin Cancer (Japan) 2022 ; 37 : 162－166]