Five-year survival results of subcutaneous low-dose immunotherapy with interleukin-2 alone in metastatic renal cell cancer patients.

After the discovery of its essential role in anticancer immunity, IL-2 cancer immunotherapy has shown that comparable results may be obtained with different schedules, including intravenous high-dose IL-2 as a bolus or as a 24-hour intravenous infusion or prolonged subcutaneous injection of low-dose IL-2 with or without IFN-alpha. This study shows the long-term results obtained in 92 metastatic renal cell cancer (RCC) patients with low-dose subcutaneous IL-2, which was given at 3 million IU twice/day for 5 days/week for 6 consecutive weeks. In nonprogressing patients, a second cycle was planned after a 21-day rest period, followed by maintenance therapy consisting of 5 days of treatment every month until disease progression. Complete response (CR) was achieved in only 2/92 (2%) patients, and partial response (PR) was observed in 19 patients (21%). Therefore, the response rate (CR + PR) was 21/92 (23%), with a median duration of response of 25 months. Stable disease (SD) occurred in 37 patients (40%), whereas the other 34 (37%) had a progressive disease (PD). The response rate was significantly higher in patients with a disease-free interval of >1 year than in those with a lower interval, in patients with a high performance status (PS) than in those with a low PS, and in patients with sites of disease other than the liver. A 5-year survival was obtained in 9/92 (9%) patients, and the percent of survival was significantly higher in patients with a response or SD than in those with PD. The treatment was well tolerated in all patients. This study confirms that low-dose subcutaneous IL-2 alone in an effective and well tolerated therapy of metastatic RCC, with results comparable to those described with more aggressive and toxic IL-2 schedules.