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Study: Two drugs may worsen colon cancer, not help it

By Stephanie Nano
Associated Press / February 5, 2009
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NEW YORK - Doctors thought that combining two newer drugs that more precisely attack cancer would help people with advanced colon cancer. Instead, it made the cancer worse and made the patients more miserable, a study found.

The surprising findings underscore the importance of doing rigorous studies before rushing to mix these pricey, new-generation drugs, the Dutch researchers and other specialists said. The doctors tried combining Erbitux and Avastin because lab tests and an earlier small study had shown promising results.

"This will stand out as a warning," said Dr. Cornelis Punt, the study's leader. "You have to do the randomized studies to see what really happens."

For the study, Eli Lilly & Co.'s Erbitux was added to standard treatment, which includes Genentech Inc.'s Avastin.

Since both are "targeted" drugs and attack tumors in different ways, the thinking was that the combo would do a better job of keeping the cancer from growing.

But the results show "more is not always better," said Dr. Robert Mayer, of Dana-Farber Cancer Institute. He wrote an editorial published with the study in today's New England Journal of Medicine.

What makes the results even more compelling, Mayer said, is that another similar study reached the same conclusion. That study, released in December, tested another targeted drug that works the same way as Erbitux.

"This is the first time we've seen harm by combining targeted therapies and it tells us we need to be cautious," said Dr. Jordan Berlin, a gastrointestinal cancer specialist at Vanderbilt-Ingram Cancer Center in Nashville.

Berlin, who had no role in the research, stressed that the drugs do help patients, just not when given together.

Colorectal cancer is the nation's second leading cancer killer. The disease was expected to kill almost 50,000 Americans last year although death rates are dropping because of screening and better treatment.

The research was done at hospitals throughout the Netherlands and led by Punt at Radboud University Nijmegen Medical Center. The 755 study patients had colon cancer that had spread. They all received Avastin, also known as bevacizumab, and two chemotherapy drugs. Half of them also got Erbitux, also called cetuximab. They were followed for nearly two years.

The group that got Erbitux saw their cancer get worse sooner, the researchers found. On average, their cancer progressed after 9.4 months compared with 10.7 months for those who didn't get Erbitux. The Erbitux group also had lower quality-of-life scores.

The overall survival in both groups was about the same.

Punt said they are now trying to figure out why the combo didn't work; it could be an interaction between these two specific drugs, Erbitux and Avastin.

After the study began in 2006, it was shown that Erbitux didn't help colon cancer patients who had a specific gene mutation.

The Dutch researchers said their study confirmed that - the worst results were in those with the mutation who got Erbitux.

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