Metastatic melanoma with initial ctDNA decline and radiographic response during self-directed antiparasitic use: treatment effect or spontaneous regression?

A 74-year-old man with nodular melanoma and nodal and liver metastases declined guideline-directed therapy and took ivermectin and fenbendazole with lifestyle changes; his disease initially showed reduced metabolic activity and size on imaging and his tumour-informed ctDNA fell from 2.04 to 0.18 MTM/mL, then both worsened, with ctDNA rising to 0.93 MTM/mL and the dominant axillary mass growing (Cheng melanoma case report 2026). The tumour carried at least 50 mutations per megabase, placing it at the extreme immunogenic end of the spectrum, and the authors write that spontaneous immune-mediated regression is at least as plausible as any effect of the patient's interventions, that clinical evidence for efficacy is absent, and that safety counselling is needed given the drugs' reported toxicities (Cheng melanoma case report 2026).