“Until just a few years ago there were no promising drugs for kidney cancer. Now there are two that have recently been approved by the FDA, and several more that are looking very good in clinical trials,” said Gary R. Hudes, MD, Director of the Genitourinary Malignancy Program at Fox Chase Cancer Center, and the study’s lead author.

“Temsirolimus is the first of these new agents to show an overall survival advantage for kidney cancer. In addition, this was the first study focusing exclusively on patients whose cancer was so advanced they would not qualify for most other clinical trials.”

Temsirolimus is a targeted inhibitor of mTOR, a signaling protein that regulates cell growth and angiogenesis. Increased, unregulated angiogenesis is characteristic of renal cell carcinoma.

Smaller, preliminary studies in patients with advanced kidney cancer that had grown or progressed with prior treatments showed that temsirolimus could slow or arrest further growth of the tumor, sometimes causing tumor regression. The physicians involved in these studies were impressed that even patients with the most advanced tumors and shortest life expectancy seemed to benefit.

The current, international study had three treatment arms. All patients had advanced, metastatic renal cell carcinoma and a poor prognosis based on a standard set of criteria. A total of 207 patients received interferon-alpha, 209 received temsirolimus, and 210 received both drugs. (Temsirolimus was given at a lower dose in the combination group.)

Median overall survival for the three groups was 7.3 months, 10.9 months, and 8.4 months, respectively. Progression-free survival was 1.9 months, 3.7 months, and 3.7 months, respectively. Typical overall survival for this high-risk group of patients with advanced kidney cancer patients is less than 6 months.

The most common side effect in all groups was weakness and fatigue, although the incidence was lower for the temsirolimus arm. Due to its mechanism of action, temsirolimus had some other unique side effects such as rashes and increased blood glucose, but they were not severe and were easily controlled.

According to Dr. Hudes, the long-term goal for the emerging new class of targeted agents for kidney cancer is to determine the optimal way to administer them, either in combination or sequentially, to provide patients with the maximum benefit.