Chronic Effects of Subcutaneous Interleukin-2 Therapy on Soluble Interleukin-2 Receptors in Advanced Small Cell Lung Cancer

The increase in IL-2 receptor serum levels is one of the most typical changes in immune parameters during IL-2 cancer immunotherapy. To better define the effects of prolonged IL-2 injection on SIL-2R levels, we evaluated 7 advanced small cell lung cancer patients who received IL-2 subcutaneously at a daily dose of 9x10⁶ IU/m²/12h for two days followed by 3x10⁶ IU/m²/12h for 18 days (5 days/week for 4 weeks). Moreover, four patients were also evaluated during the second IL-2 cycle. Venous blood samples were drawn before and at weekly intervals during IL-2 therapy. Mean SIL-2R serum levels rapidly increased with the start of IL-2 injection, and they were signicantly higher than the baseline levels throughout the immunotherapy cycle. The increase in mean SIL-2R levels was higher in patients with progressive disease than in those with response or stable disease, but the difference was not significant. Finally, the increase in mean SIL-2R concentrations during the second IL-2 cycle was not significantly different from that seen during the first one. The present study confirms that IL-2 administration determines an evident increase in SIL-2R levels; moreover, it would demonstrate that re-exposure to IL-2 after a rest period does not induce a more pronounced SIL-2R release.