Aims and background: IGF-1 has been proven to be one of the most important growth factors for normal and neoplastic cells. Abnormally high levels of IGF-1 have been observed in cancer patients. Since it has been demonstrated that some growth factors may counteract the action of antitumor cytokines, the presence of increased IGF-1 concentrations could reduce the efficacy of cancer biotherapies with cytokines, such as IL-2. The present study was performed to evaluate the efficacy of IL-2 immunotherapy in relation to the pretreatment levels of IGF-1 in advanced cancer patients.
Methods: The study included 20 consecutive patients with metastatic renal cell cancer who were treated subcutaneously with IL-2 at 6 million IU/day for 5 days/week for 6 weeks. IGF-1 serum levels were measured by RIA on venous blood samples collected before the immunotherapy, after 3 weeks, and at the end of IL-2 injection.
Results: Objective tumor regressions were obtained in 5/20 patients, consisting of 1 complete response (CR) and 4 partial responses (PR). Nine patients had stable disease and the last 6 patients progressed. Abnormally high pretreatment levels of IGF-1 were seen in 13/20 patients. The percent of clinical responses (CR + PR) was significantly higher in patients with normal pretreatment concentrations of IGF-1 than in those with elevated levels (4/7 vs 1/13, P < 0.01). No significant changes in mean IGF-1 levels occurred during IL-2 therapy. However, mean IGF-1 levels increased in progressing patients and decreased in those with a response or stable disease, even though none of the differences was statistically significant.
Conclusions: The study showed that high pretreatment levels of IGF-1 are associated with a reduced efficacy of IL-2 immunotherapy of renal cancer. Further studies are required to establish whether IGF-1 levels simply reflect the extension of disease, or whether they may influence per se the action of IL-2.