Background: PROCLAIM^SM (www.proclaimregistry.com) is an IL-2 registry with over 40 participating sites with a retrospective (retro) (N = 97, locked) and prospective cohort (N > 400 on-going). Previously, we reported a median overall survival (mOS) of 50.9 months (mo) with a median follow-up of 37.1 mo in mRCC patients treated with HD IL-2 between 2007 and 2012 from the retro cohort (ASCO 2014). Here we update survival and report on the prospective cohort. Methods: Inclusion criteria required patients receive at least one dose of IL-2. IRBs waived consent for retro patients, therefore post IL-2 treatment data is unavailable. Prospective patients received their first dose of HD IL-2 prior to 2013 with post IL-2 treatment data collected. Survival for both cohorts is current to January 2015. Results: The overall response rate (ORR) for the 123 patients in the prospective cohort is 17.9%. Complete response (CR), partial response (PR), and stable disease (SD) patients have a 2.5 year survival rate of 100%, 87%, and 73% respectively. The mOS is 29.6 mo at a median follow-up of 23.2 mo. The mOS was not reached (NR) in patients treated with only HD IL-2 and was 13.1, and 29.6 mo in those who had prior or post TT (Table 1). The treatment-related mortality rate in the combined retro and prospective cohorts is 0.9% (4/435). Conclusions: PROCLAIM prospective and retro cohorts demonstrate that SD, previously grouped with the non-responders, has high survival rates. Although limited by numbers (15 patients), TT prior to IL-2 data appears less desirable. These data support that HD IL-2 has favorable safety profile compared to data in the original package insert and is effective first line therapy for eligible patients with mRCC. Clinical trial information: NCT00686959