COMPLETE RESPONSE OF MELANOMA-IN-TRANSIT METASTASIS AFTER ISOLATED LIMB PERFUSION WITH TUMOR-NECROSIS-FACTOR-ALPHA AND MELPHALAN WITHOUT MASSIVE TUMOR NECROSIS - A CLINICAL AND HISTOPATHOLOGICAL STUDY OF THE DELAYED-TYPE REACTION PATTERN

Treatment of stage IIIA/B melanoma patients by isolated limb perfusion (ILP) with a combination of tumor necrosis factor-alpha (TNF-alpha) a nd melphalan induces a complete response in 80-90% of the cases, The m echanism of tumor regression induced by the combination of TNF-a! and melphalan is not precisely understood. Previous studies focused on the immediate (i.e., within a few days) clinico-pathological changes afte r perfusion involving hemorrhagic necrosis, However, clinical data cle arly indicate that complete tumor remission frequently requires a peri od of a few weeks to as much as months after ILP. Because the mechanis m underlying this delayed-type reaction is completely unknown, we stud ied the clinico-pathological events in patients with such slowly regre ssing melanoma lesions. For this purpose, 94 biopsies of in-transit me lanoma metastasis that were taken sequentially from 11 patients betwee n 1 week and 9 months after ILP were analyzed by light and electron mi croscopy and immunohistochemistry. Clinical data included patient sex, age, anatomical localization and size of the tumor, and follow-up. Al l of the 11 patients ultimately responded to perfusion treatment (9 co mplete, 1 partial, 1 stable disease), Serial biopsies showed scattered individual tumor cell necrosis without hemorrhage. Most of the lesion s with this delayed-type reaction pattern were less than 0.5 cm in dia meter, They contained varying amounts of histologically viable-looking tumor cells and tumor-infiltrating melanophages, In addition, a marke d but transient infiltrate of peritumoral eosinophils and moderate int erstitial edema and dermal fibrosis were encountered. Only small numbe rs of lymphocytes were present. In comparison with the reaction patter n after treatment with melphalan alone, the delayed-type reaction patt ern was similar but more intense, The scattered tumor cell necrosis in the latter type may be explained by a TNF-alpha-induced increase in p ermeability of the tumor vascular bed, which results In higher intratu moral concentrations of melphalan or in a prolongation of its effect. Subsequently, degenerated tumor cells are cleared by macrophages, and, finally, repair by fibrosis occurs, Because the immediate reaction ty pe is evoked by hyperpermeability of the tumor vessels as well, quanti tative differences seem to determine which reaction type ensues, We su ggest that the extent of tumor vasculature that is sensitive to TNF-al pha determines the onset and histopathological pattern of tumor regres sion after ILP.