Failed Avastin early-stage cancer study detailed

ORLANDO, Florida (Reuters) - A study of blockbuster drug Avastin in colon cancer patients who have undergone surgery showed that the drug's effectiveness wore off after patients stopped taking it, researchers said on Saturday.

As previously disclosed by the drug's maker, Roche Holding AG's Genentech unit, the 2,710-patient trial did not meet its main goal of showing an extension in disease-free survival.

Newly released details show that 77.4 percent of patients in the Avastin group were alive and free of disease after a median follow-up of three years, compared with 75.5 percent of patients in the control group, a difference that was not statistically significant.

But at the one-year mark, Avastin was shown to reduce the risk of cancer recurrence or death by about 40 percent. This result proves that the drug is active in early-stage cancer, said Phillippe Bishop, head of clinical development for Avastin at Genentech.

The trial was designed to show whether use of Avastin plus chemotherapy for six months, followed by six months of Avastin alone, results in more patients being cancer free after three years compared with just treating them with chemotherapy.

"As patients come off treatment, the events come back," Bishop said. "The one-year duration of treatment was insufficient to derive clinical benefit."

This was the first trial which sought to show Avastin's ability to prevent cancer recurrence by wiping out microscopic cancer cells that may remain in the body after tumors have been removed by surgery, known as use in the "adjuvant" setting. But several similar trials are under way, including a second in early-stage colon cancer patients for which results are expected next year.

Since all of the current adjuvant trials of Avastin also have treatment durations of one year, there is little expectation that results will be encouraging.

Bishop said the latest findings, presented here at a meeting of the American Society of Clinical Oncology, are influencing Roche/Genentech's ongoing clinical trial program for Avastin.

The drug, known chemically as bevacizumab, is an antibody designed to fight cancer by interfering with the blood supply to tumors. A month of Avastin treatment costs about $4,400.

The drug, which has annual sales of about $4.4 billion, is currently approved for treating metastatic colorectal, breast, lung and later-stage brain cancers.

Use in earlier-stage cancer patients would drive even more sales.

"There was a transient benefit in disease-free survival during the one year that bevacizumab was given," said Dr Norman Wolmark, chairman of the Department of Human Oncology at Allegheny General Hospital and the study's lead author.

The trial was conducted by the National Surgical Adjuvant Breast and Bowel Project group and was funded by the National Cancer Institute.

"We hope to start a trial in the not too distant future where we use bevacizumab for a period of two years," Wolmark said.

(Reporting by Deena Beasley, editing by Eric Beech)