Provenge (sipuleucel-T), by Dendreon Pharmaceuticals, is superior to Zytiga (abiraterone acetate) or Xtandi (enzalutamide) at prolonging the lives of men with metastatic castration-resistant prostate cancer (mCRPC) when added at any point in a treatment regimen, according to a real-life study in the U.S.
The study, “A Retrospective Observational Analysis of Overall Survival with Sipuleucel-T in Medicare Beneficiaries Treated for Advanced Prostate Cancer,” was published in the journal Advances in Therapy.
“Men with mCRPC who received [Provenge] had a significant improvement in median overall survival and reduction in the risk of death at three years, regardless of line of use,” Rana R. McKay, MD, the study’s lead author, said in a press release. McKay is a medical oncologist and assistant professor of medicine at Moores Cancer Center, University of California San Diego.
“This analysis underscores the importance of using complementary mechanisms of action to maximize patient survival outcomes and highlights the critical role immunotherapy plays in the modern era of mCRPC treatment,” said Bruce A. Brown, MD, Dendreon’s chief medical officer.
“Provenge continues to deliver on its promise of helping men with advanced prostate cancer live longer and should be considered when making treatment decisions in daily clinical practice,” Brown added.
Approved in the U.S. in 2010, Provenge is the only immunotherapy that uses a patient’s own immune cells to fight prostate cancer. It consists of an individual’s white blood cells that have been exposed to a prostate cancer protein, ultimately priming them to activate the remaining immune cells to fight cancer.
In the years since Provenge’s approval, the oral agents Zytiga and Xtandi — second-generation androgen-receptor signaling pathway inhibitors (ASPIs) — have become the standard-of-care treatment for men with mCRPC. Currently, both ASPIs and Provenge are recommended as a first-line treatment for the same indication.
However, no study to date has compared the effectiveness of Provenge with that of the ASPIs.
To fill this knowledge gap, Dendreon researchers and colleagues retrospectively analyzed the survival outcomes of 6,044 men with mCRPC who received either Provenge or ASPIs (Zytiga or Xtandi). The investigators used the Medicare 100% dataset from 2013 to 2017.
This real-life dataset provides U.S. longitudinal claims data that can be linked to survival outcomes from a large contemporary patient population.
Included patients had not received prior chemotherapy for their mCRPC. Their median age ranged from 75 to 79, and more than 80% of them were white. The men were divided into two study groups for two different survival analyses at three years: first-line treatment and any-line treatment.
The first analysis compared the survival outcomes of 647 men who received first-line Provenge versus 4,810 who were given first-line ASPIs. Of note, men in either group were able to receive any other approved therapy for mCRPC in subsequent treatment lines.
Similarly, the second analysis compared the survival outcomes of 906 men given Provenge at any point in their treatment regimen versus 5,092 men who received ASPIs but never received Provenge.
The most frequently used treatments in the first-line setting were Zytiga (55.9%), Xtandi (24.3%), and Provenge (10.8%). Most (75%) men receiving ASPIs in any line without Provenge had one or two lines of treatment, while 55% of those receiving Provenge at any time received two to three therapy lines. Among men treated with Provenge, most (71%) received it in the first-line setting.
Provenge-treated men were slightly younger than those receiving ASPIs, and fewer of them were covered by both Medicare and Medicaid insurance, which the researchers noted was generally an indirect indicator of a lower socioeconomic status and more complex health needs.
Initial results, presented at the American Society of Clinical Oncology (ASCO) 2020 Genitourinary Cancers Symposium, held online, suggested a 45% drop in the risk of death and a 14-month survival benefit with any-line Provenge, compared with any-line ASPIs without Provenge.
The current study explored differences in the survival outcomes, adjusted for multiple factors available in the dataset that could potentially influence the patients’ risk of death.
The results showed that men treated with first-line Provenge lived significantly longer (34.9 months; nearly three years) than those receiving ASPIs as first-line therapy (21 months; just less than two years), reflecting a 44% reduced risk of death at three years.
Further, adding Provenge to either Zytiga or Xtandi at any point of the treatment regimen reduced the risk of death by 41% and prolonged median overall survival by 14.5 months (just over one year). Specifically, overall survival was 35.2 months with any-line Provenge versus 20.7 months without the immunotherapy.
These findings highlight that including Provenge at any point during treatment prolongs the life of men with mCRPC by more than one year and reduces their risk of death by more than 40%.
While safety was not a focus of the analysis, first-line treatment with Provenge also resulted in fewer emergency visits, related or not to prostate cancer, in the first year of treatment, compared with ASPIs.
Moreover, exploratory analyses suggested that patients who received both Provenge and an ASPI during their treatments saw their risk of death reduced by 52% compared with only one ASPI or two sequential ASPIs.
“These findings support the need for further research to explore treatment sequences and therapeutic layering [combinations],” the researchers wrote.
McKay said that “these data contribute to a growing body of evidence demonstrating the real-world effectiveness of [Provenge] in the mCRPC patient.”
The team noted, however, that further studies and trials are needed to confirm these findings and improve treatment recommendations for men with mCRPC.
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