IL2 and metastatic melanoma: For example, in a retrospective study of 371 metastatic melanoma patients treated with the first FDA-approved “modern” immunotherapy high-dose IL-2, the response rate in patients with cutaneous or subcutaneous metastasis was ~ 50% whereas with visceral metastases it was only 13%; more strikingly, in individual patients harboring both cutaneous/subcutaneous and visceral metastases, tumor regression took place only at cutaneous/subcutaneous lesions whereas visceral metastases progressed upon the same systemic IL-2 therapy [25].