High dose (HD) IL-2 for metastatic renal cell carcinoma (mRCC) in the targeted therapy era: Extension of OS benefits beyond complete response (CR) and partial response (PR).

Abstract

423 Background: HD IL-2 has been reported to have a overall response rate (ORR) for mRCC of 15% and a median OS of 19 months (Fyfe, 1995), however, the studies that led to its regulatory approval are >15 years old and were performed in an era preceding targeted therapies. Methods: The PROCLAIM registry (www.proclaimregistry.com), a HD IL-2 observational database currently with over 30 participating sites, consists of a retrospective cohort (treated between 2007 and 2012) informing an ongoing prospective cohort (~600 patients). We report on the retrospective mRCC subjects (n=97, 13 sites) with survival status determined as of November 2013 and a median follow-up of 32 months. Sites were encouraged to enroll patients sequentially. Inclusion criteria required that patients have received at least one dose of HD IL-2. Results: The ORR was 22% (8% CR and 14% PR). Of 97 subjects, 36 were confirmed deceased and 61 were known to be alive, none were lost to follow-up. The median OS was 51 months, compared to a median OS range of 5-35 months for FDA-approved targeted agents (Harrison, 2013). There was significant clinical benefit in patients with CR, PR, and stable disease (SD), none of which reached median OS compared to 37.9 months in patients with progressive disease (PD). There is a significant advantage in PROCLAIM for those patients treated 1st vs. 2nd line HD IL-2; the median OS was 61.8 months (n=82) vs. 15.3 months (n=15), respectively. The clinical benefit of HD IL-2 therapy as front line is consistent with published data (Birkhauser, 2013). No deaths due to IL-2 related toxicity were reported in the retrospective cohort. Conclusions: The PROCLAIM registry documents a vastly improved OS for HD IL-2 compared to historical results during a time interval marked by the advent of targeted therapy for advanced RCC. Response to IL-2 (CR or PR) is associated with prolonged survival, however, stable disease as well as front line use also appears to positively impact survival. Issues including patient selection characteristics and treatment sequencing are hypotheses currently being explored in the prospective database. Clinical trial information: NCT01415167.