Case Report: 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 of the right lateral neck presented with nodal and hepatic metastases at staging. He declined guideline-directed therapy and instead pursued lifestyle modifications alongside self-administered ivermectin and fenbendazole. On serial imaging, his disease initially demonstrated reduced metabolic activity and size without new sites of involvement, paralleled by a decline in tumor-informed ctDNA (Signatera) from 2.04 to 0.18 MTM/mL. Both subsequently worsened, with ctDNA rising to 0.93 MTM/mL and the dominant axillary nodal mass increasing in size and avidity. The tumor carried a mutational burden of at least 50 mutations/Mb, placing it at the extreme upper end of the immunogenic spectrum, and spontaneous immune-mediated regression is at least as plausible an explanation as any effect of the patient's interventions. The discussion contextualizes the growing popularity of antiparasitic repurposing in oncology, the absence of clinical evidence supporting efficacy, and the need for safety counseling given the reported toxicities of such drugs.