Improved survival and tumor control with Interleukin-2 is associated with the development of immune-related adverse events: data from the PROCLAIM

BACKGROUND: Immune related adverse events (irAEs) are associated with immunotherapy for cancer and while results suggest improvement in tumor control and overall survival in those experiencing irAEs, the long-term impact is debated. We evaluated irAE reports related to high dose interleukin-2 therapy (IL-2) documented in the PROCLAIM METHODS: Reports on 1535 patients, including 623 with metastatic melanoma (mM) and 919 with metastatic renal cell cancer (mRCC) (7 patients had both diseases), were queried for irAEs. The timing of the event was categorized as occurring before, during or after IL-2 or related to any checkpoint inhibitor (CPI). mM patients and mRCC patients were analyzed separately. Tumor control [complete + partial response + stable disease (CR + PR + SD) was compared between those experiencing no irAE versus those with the development of irAEs. Survival was analyzed by tumor type related to timing of irAE and IL-2, and in those with or without exposure to CPI. RESULTS: Median follow-up was 3.5+ years (range 1-8+ years), 152 irAEs were reported in 130 patients (8.4% of all PROCLAIM CONCLUSIONS: irAEs following IL-2 therapy are associated with improved tumor control and overall survival. IrAEs resulting from IL-2 and from CPIs are qualitatively different, and likely reflect different mechanisms of action of immune activation and response