Adding the targeted drug Avastin (bevacizumab) to interferon delays the progress of metastatic kidney cancer longer than interferon alone, according to new research presented at the annual meeting of the American Society of Clinical Oncology.

It took more than 10 months for tumors to begin growing again in people treated with Avastin, compared to a little over 5 months for people in the interferon group.

The results from the research team's first analysis were so impressive, they switched all patients in the study into the Avastin group, said lead researcher Bernard Escudier, MD, of France's Institute Gustave-Roussy.

Until then, the 649 patients in the study had been divided into 2 groups: one treated with interferon alone, and one treated with interferon plus Avastin. All of the participants had clear cell renal carcinoma (the most common form of kidney cancer) that had spread to other parts of the body.

Nearly one-third of the patients assigned to Avastin treatment -- 31% -- had their tumors shrink in response to the drug. In the interferon-alone group, only 13% responded.

The side effects were what researchers expected -- the typical side effects seen with each of the drugs. Avastin caused more high blood pressure and protein in the urine than interferon. Fatigue was a little worse than expected, but Escudier said that might have been due to the high dosages used in the study.

Avastin is not officially approved for use in kidney cancer patients, but is approved for treatment of advanced colon cancer and non-small cell lung cancer.

The study could not determine whether Avastin helped kidney cancer patients live longer, but Escudier said there was a trend toward better survival with Avastin.

Now, researchers must determine how Avastin compares to other recently approved drugs for kidney cancer. The drug Torisel (temsirolimus) was approved last week after research showed it does help people with late-stage disease live longer. Nexavar (sorafenib) has been shown to delay the time it takes for cancer to start growing again, while Sutent (sunitinib) also delays tumor growth and shrinks tumors.

"We're in a very exciting time in kidney cancer research, with a number of new targeted therapies becoming available," said Escudier. "This study shows the efficacy of yet another agent with the added benefit of a strong safety profile."

Citation: "A randomized, controlled, double-blind phase III study (AVOREN) of bevacizumab/interferon-á2a vs. placebo/interferon-á2a as first-line therapy in metastatic renal cell carcinoma." Presented June 4, 2007, at the annual meeting of the American Society of Clinical Oncology. First author: Bernard Escudier, MD, Institute Gustave Roussy, France.