BIOLOGICAL SIGNIFICANCE OF INTERLEUKIN-6 SECRETION ON CANCER-IMMUNOTHERAPY WITH INTERLEUKIN-2

It is known that IL-6 may influence the antitumour efficacy of IL-2. H owever, the prognostic significance of IL-6 blood concentrations durin g cancer immunotherapy with IL-2 needs to be better understood. This p reliminary study was performed to evaluate the efficacy of IL-2 cancer immunotherapy in relation either to the pretreatment levels of IL-6, or to its variations on IL-2 therapy. The study included 13 evaluable metastatic renal cancer patients, who underwent low-dose IL-2 subcutan eous immunotherapy (3 x 10(6) IU/day for 6 days/week for 4 weeks). In non-progressing patients, a second cycle of IL-2 was given after a 21- day rest period. Serum levels of IL-6 were measured by ELISA before th e onset of therapy and at weekly intervals on IL-2 injection. Abnormal ly high pretreatment blood levels of IL-6 were observed in 6 out of 13 patients. A partial response (PR) was obtained in 2 patients. A stabl e disease (SD) was achieved in another 6 patients, whereas the remaini ng 5 cases progressed. IL-6 mean pretreatment levels were significantl y higher in progressing patients than in those with PR or SD. No signi ficant variation in IL-6 mean levels occurred on IL-2 administration, and no significant difference in IL-6 variations was seen between the first and the second cycle of IL-2. This study shows that the evidence of high levels of IL-6 before therapy is associated with lack of effi cacy of IL-2 cancer immunotherapy, whereas changes in IL-6 levels duri ng IL-2 administration would have no prognostic significance.