NEW YORK, July 6 (UPI) -- The cancer medication Avastin has been called a wonder drug, but may be less effective than U.S. regulators believed when they approved it.

Made by Genentech, Avastin, or bevacizumab, was approved by the U.S. Food and Drug Administration for the use in patients with advanced lung, colon or breast cancer. It works by cutting off tumors' blood supply, The New York Times (NYSE:NYT) reported Sunday.

In 2004, the medication was approved for combination use with chemotherapy for metastatic colon cancer and non-small cell lung cancer. It was approved this year for treatment in breast cancer.

The medication, which can cost $100,000 a year, may prolong life by only a few months.

Dr. Leonard Saltz, a colon cancer specialist at Memorial Sloan-Kettering Cancer Center in New York, said the "incremental benefit" of Avastin "may be more modest than we want to admit."

Some patient advocates have said they are concerned by costly treatments like Avastin coming into routine use.

"It's absolutely critical that we start having a public discussion," said Barbara Brenner, executive director of advocacy group Breast Cancer Action. "I think of Avastin as a model that is showing us where the problem is."