3074 Background: F. Recchia et al. (Interleukin-2 and 13-cis retinoic acid in the treatment of minimal residual disease: A phase II study. Int J Oncol. 20: 1275-1282, 2002) previously defined the possibility of achieving a chronic immune stimulation through a prolonged low dose sc interleukin 2 (IL2)-based schedule, leading to a prolongation of PFS in advanced cancer patients (pts). A confirmatory phase II study was started. Methods: Pts diagnosed of high risk solid tumors in response to chemotherapy were included. RIS consisted in low dose IL2 (1.8 MU sc per day, 5 days per week, 3 weeks per month) plus oral isotreonin (CRA, 0.5 mg/kg) the same days of IL2 and/or sc PEG-interferon (50 µg per week of treatment). No Chx was allowed with RIS, but concurrent maintenance with TKI or Hx was permitted. Results: Since 08/2007 to 01/2013, 69 pts (39 M/30 F, median age 60 y, range 31-78) were included. 51 pts were treated with stage IV disease. 36 pts entered in complete response (CR), 29 in partial response (PR), 1 with progressive disease, 3 adjuvant. 4/69 grade 3/4 toxicity, (6%): 1 fatal poliserositis resistant to cortisone after 20 months of RIS, 1 stopped RIS for reaction requiring steroids, 1 for multiinfarction dementia, 1 for grade 3 liver toxicity. 3 pts presented other alterations managed along the course of the RIS (1 PVT, 1 ITP, 1 angina resolved after stent placement). Grade 1-2 fever, fatigue and joint pain were commonly observed but usually controlled with NSAIDs. Among the 68 pts evaluable for response, one pt progressed, 26 presented stable disease (median TTP 3 mo, range 2-28), 3 presented PR (1 melanoma, 1 prostatic ca, 1 ovarian ca; 9, 11 and 28 mo respectively), and 38 maintained or presented CR (median TTP 19 mo, range 2-62+). Three pts in PR were converted to a CR during RIS (1 pancreatic ca, 1 ovarian ca, 1 larynx ca). Conclusions: In this study we confirm the previous results reported by F. Recchia et al. RIS represents a good alternative for high risk pts with solid tumors after systemic chemotherapy induced response with acceptable tolerability and offers in selected pts a possibility of obtaining a CR after a PR. Further validation and randomized studies are warranted.