CLINICAL-RESPONSES AND LYMPHOID INFILTRATES IN METASTATIC MELANOMA FOLLOWING TREATMENT WITH INTRALESIONAL GM-CSF

Past studies in animal models with gene-transfected tumour cells have suggested that GM-CSF may have a role in immunotherapy of tumours as a result of the effects it has on antigen-presenting cells. The present (phase I) studies were carried out to examine whether intralesional i njections of GM-CSF induce regression of subcutaneous metastases in pa tients with melanoma and influence lymphoid infiltrates in and around the metastases. Thirteen patients had 15-50 mg doses of GM-CSF injecte d into two subcutaneous metastases. In each case one metastasis receiv ed only five injections before excision whereas the other received wee kly injections up to 6 months. Partial regression of injected and/or n on-injected metastases was seen in three patients. The metastases from the responding patients that were treated with intralesional GM-CSF h ad marked increases and high absolute numbers of T cell infiltrates in to the tumour, particularly of the CD4 T cell subset. There was an inc rease in IL-2R expression on the T cells and an increase in the number of Langerhans' cells infiltrating the tumours. The best predictors of clinical responses therefore appeared to be high relative increases a nd high absolute numbers of CD4 + T cells and Langerhans' cells within the treated tumour. These results provide support for further explora tion of the role of GM-CSF in immunotherapy of human melanoma.