SAN FRANCISCO – Tyrosine kinase inhibitors that target the vascular endothelial growth factor receptor increase the risk of a fatal adverse event in cancer patients, but the absolute rate is still low, investigators concluded from a meta-analysis of 10 randomized trials with a total of 4,679 patients.
Trial participants given sorafenib (Nexavar), sunitinib (Sutent), or pazopanib (Votrient) were more than twice as likely to die from an adverse event as were peers given control treatment, said lead investigator Dr. Christopher J. Richards of the Beth Israel Deaconess Medical Center in Boston. Yet, the rate was still less than 2%.
Dr. Christopher J. Richards
"Our analysis may underestimate the true incidence of fatal adverse events, as study patients may be healthier than the general population exposed to these drugs," he noted at the Genitourinary Cancers Symposium. But that said, "all three of the study drugs have been shown in various randomized controlled trials to improve clinical outcomes compared to traditional therapies."
Discussant Dr. Thomas E. Hutson of the Baylor Sammons Cancer Center in Dallas commented, "I feel confident that everyone or almost everyone in the room today would agree with me that our current therapy benefit outweighs the risk associated with the treatment."
Moreover, even among the new targeted agents, the 1.5% rate seen with the vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKIs) in the meta-analysis "compares very favorably" with the rate of 2.9% seen previously with bevacizumab (Avastin), another VEGF-targeted therapy, in a similar analysis (JAMA 2011;305:487-94).
"Targeted therapies have real toxicities, and these toxicities include a low risk of death – a risk of death not much different than other therapies used for kidney and other cancer types," Dr. Hutson asserted. "If anything, this meta-analysis shows us that close monitoring is going to be essential for optimal use of these agents."
In the study, Dr. Richards and his colleagues identified 10 randomized controlled phase II or III trials in which patients received any of three VEGFR TKIs approved by the Food and Drug Administration for cancer treatment as of February 2011: sorafenib, sunitinib, or pazopanib. The control groups were usually treated with a placebo, but in some cases with chemotherapy or immunotherapy.
Dr. Thomas E. Hutson
The enrolled patients had a variety of malignancies: renal cell carcinoma, hepatocellular carcinoma, melanoma, non–small cell lung cancer, breast cancer, and pancreatic neuroendocrine tumor. "All patients included in the studies had good performance status and had adequate baseline cardiac, hematologic, and renal function at the time of study entry," Dr. Richards pointed out.
In a pooled analysis, relative to control treatment, VEGFR TKI treatment was associated with a 2.23-fold increased risk of fatal adverse events (P = .02). But even so, the absolute rate of such events was just 1.5%, compared with 0.7% with the control treatment.
In stratified analyses, there was no significant difference in the relative risks across the three agents or the relative risks for renal cell carcinoma vs. other types of cancer.
The most common fatal adverse events in the trials overall (considering both control and VEGFR TKI arms) were hemorrhage (48% of the total), myocardial infarction (15%), and hepatic failure (10%). These events "occurred in both the placebo and control groups as well as study groups," Dr. Richards noted.
He acknowledged that limitations of the study included the fact that the analysis used study-level instead of patient-level data, which may have resulted in confounding, and that it did not have adequate power to detect differences between the three VEGFR TKIs, although they all have a similar mechanism of action.
The symposium was sponsored by the American Society of Clinical Oncology, the American Society for Radiation Oncology, and the Society of Urologic Oncology.
Dr. Richards disclosed that he had no relevant conflicts of interest. Dr. Hutson disclosed that he is a consultant to and receives honoraria from Bayer, Genentech, GlaxoSmithKline, Novartis, Onyx, Pfizer, and Wyeth, and that he receives research funding from GlaxoSmithKline, Pfizer, and Wyeth.