Metastatic RCC: High-dose IL-2 ups overall survival

High-dose interleukin-2 shows overall survival benefits in metastatic renal cell carcinoma that extend beyond complete and partial responders, researchers reported at the American Society of Clinical Oncology annual meeting in Chicago.

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The retrospective analysis of the PROCLAIM patient registry found improved survival for those with stable and progressive disease after high-dose aldesleukin (Proleukin) in the tyrosine kinase inhibitor (TKI) era.

The analysis also found a trend favoring patients receiving first-line versus second-line high-dose IL-2 immunotherapy, suggesting that patient selection and drug sequencing may yield better outcomes, according to a press release from Prometheus Laboratories.

Mayer Fishman, MD, PhD, of Moffitt Cancer Center in Tampa, FL, is familiar with the registry. Moffitt is among the 35 participating sites in the registry, which includes RCC and melanoma patients.

The main message for urologists is that although a relatively small fraction of patients gets HD IL-2, the fraction of those patients who have relatively good survival is not limited only to those with major objective response.

“This type of study, which is nonrandomized and observational, cannot establish whether it is the patient selection or the specific treatment which results in this observation of relatively good survival,” said Dr. Fishman, who was not a study author. “However, among the patients treated with interleukin-2, the survival that is observed appears significantly better than the general kidney cancer treatment population, and this is not only seen in those with complete responses, but also among the partial response and stable disease subsets.”

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The analysis shows the patient subset with prior interleukin-2 treatment have relatively better survival compared to the general kidney cancer population, even if one counts only those with partial response and stable disease alone. That’s without the known excellent durability cancer control among those getting complete response, according to Dr. Fishman.

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“This finding is provocative because previously the bulk of the benefit was attributed to just of the complete response patients. Once again, this is not a type of study that could be conclusive about causation versus patient selection,” he said.

The data reflect an analysis of 97 U.S. patients with metastatic RCC who received at least one dose of high-dose IL-2 and were followed for a median 37.1 months. Researchers report that of 84 patients with complete data, 62 had favorable, 48 had intermediate, and three had poor prognoses.

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Overall response rate to IL-2 therapy was 22%, including 8% complete responses. The median overall survival rate from the time of high-dose IL-2 administration was 51 months, which is higher than the 19-month median survival reported in the pre-2006 National Cancer Institute series of HD IL-2 alone.

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There were no deaths due to IL-2-related toxicity reported in the retrospective PROCLAIM registry cohort, according to the Prometheus release.

“The survival in the PROCLAIM retrospective cohort exceeds the median overall survival in the studies that led to regulatory approval of IL-2 prior to the availability of TKI, suggesting that proper sequencing of IL-2 and targeted therapies may enable improved outcomes in appropriate patients,” lead investigator Michael Morse, MD, MHS, of Duke University School of Medicine, Durham, NC, said in the release. “As we continue to collect data in the prospective cohort, we hope to refine our understanding of which candidates are most likely to benefit from sequential therapy, and to use this knowledge to extend patients’ lives.”

Dr. Morse is on the speakers' bureau for Celgene, Genentech, Novartis, and Prometheus, and receives research funding from Aduro Biotech, AlphaVax, Onyx, and Prometheus. Two study co-authors are employees of Prometheus.

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