Stable disease after high dose interleukin-2 (HD IL-2) immunotherapy: observations on long term survival and clinical benefit of additional HD IL-2

Patients with stable disease (SD) following cancer treatment have traditionally not been considered responders. We, and others, have previously shown that SD is an important response criteria in cancer patients treated with HD IL-2 immunotherapy [1-5]. Here we summarize findings from 13 sites, including 97 mRCC and 170 mM patients enrolled in the retrospective cohort of a national HD IL-2 database (www.proclaimregistry.com). Patients in the database were enrolled between 2006-2011, in an era of immune checkpoint inhibitors and targeted therapies. In metastatic renal cell carcinoma (mRCC) the median overall survival (mOS) was not reached in patients assessed to have SD post HD IL-2 (Figure 1). The mOS was over 2.5 years in patients with stable disease with metastatic melanoma (mM). The median follow-up for both diseases was 3 years. We further sought to examine whether patients with SD after 1 course, received benefit with additional HD IL-2 treatment. In mRCC patients that did not respond to treatment but continued onto another cycle of HD IL-2, the mOS was not reached and was statistically significant from patients that stopped treatment (p = 0.0269) (Figure 2).