Targeted Drugs Make Gains Against Kidney Cancer
For the first time in two decades, patients are benefiting from new treatments for kidney cancer, and many physicians are optimistic about a disease that has been hard to treat and difficult to detect in its early stages.
Two targeted drugs have been approved by the Food and Drug Administration (FDA) for kidney cancer in the last 7 months - the first new therapies since biological agents were developed in the 1980s.
Over the weekend, there was more good news. At the American Society of Clinical Oncology (ASCO) annual meeting, researchers presented findings from two final-stage clinical trials that favored targeted drugs over standard therapy with interferon, the most commonly used biological agent.
"It's an exciting time," said Dr. Robert J. Motzer of Memorial Sloan-Kettering Cancer Center, who presented results from a trial involving sunitinib (Sutent). The drug was approved in January as a second-line treatment for advanced kidney cancer.
The study he presented at ASCO tested sunitinib as a first-line treatment in patients with advanced kidney cancer. The drug nearly doubled the amount of time it took for the cancer to grow or spread compared with interferon (47 weeks vs. 24 weeks).
"This is a treatment that works," said Dr. Motzer, noting that the drug is a pill patients take at home. "It has changed the whole atmosphere of my clinic."
The study cannot yet say whether sunitinib helps patients live longer. But anecdotally Dr. Motzer pointed out that several of his patients who were expected to do poorly on biological agents are doing "extremely well" more than 2 years after starting on sunitinib.
The second trial presented at ASCO asked whether an experimental intravenous drug called temsirolimus could help high-risk patients with poor prognoses live longer. The drug inhibits a protein called mTOR that regulates other proteins, some of which drive cancer.
In the study, temsirolimus increased survival among these patients (11 months) beyond what was achieved by interferon (7 months) or interferon plus temsirolimus (8.4 months).
The improvement in survival was "remarkable" considering that most high-risk patients with advanced disease live less than 6 months, said lead researcher Dr. Gary R. Hudes of the Fox Chase Cancer Center.
Following the presentations at ASCO, Dr. Michael B. Atkins of the Beth Israel Deaconess Medical Center put the new results in context.
Sunitinib, he said, could now be considered the new standard first-line treatment for advanced kidney cancer in patients with favorable or intermediate prognoses, while temsirolimus could be the new first-line treatment for patients with poor prognoses.
Sorafenib (Nexavar), which the FDA approved last December, would be the standard second-line treatment for patients who have received prior biological therapy, he said.
Asked why the new drugs seem to have appeared all at once, Dr. Motzer said that although no new treatments emerged in the 1990s, researchers identified a number of genes and proteins involved in the disease.
Some of these molecules turned out to be the targets of experimental drugs like sunitinib, and for this reason early in their development the drugs were tested against kidney cancer.
None of the targeted drugs, however, is a cure, and the disease will kill nearly 13,000 Americans this year. Tobacco use is the only known risk factor.
"This is really the beginning," said Dr. Alison Martin of NCI's Cancer Therapy Evaluation Program at ASCO.
The challenge now is to learn how best to use the drugs, she added, and to see whether these or other targeted agents provide more benefit when given in combination.
Another priority is to test single agents earlier in the disease to try to improve cure rates among high-risk patients. Toward this end, NCI and its cooperative groups, in a partnership with Pfizer and Bayer, launched a large, national clinical trial last month.
The trial, led by the Eastern Cooperative Oncology Group, will seek to answer a question raised by the success of targeted drugs: Do patients with localized disease who have had their cancers surgically removed benefit from additional treatments with sunitinib or sorafenib?
By Edward R. Winstead