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BOSTON (Reuters) - More is not always better when it comes to mixing cocktails of drugs to fight cancer, Dutch researchers reported on Wednesday.
They found that adding the ImClone drug Erbitux to an already-potent drug combination offers no additional benefit against advanced colon cancer.
In fact, patients who got Erbitux added to a three-drug combination fared worse, the researchers reported in the New England Journal of Medicine.
Researchers found that 368 volunteers who did not get the extra drug had their tumors remain stable for more than a month longer than a comparable number given Erbitux, known chemically as cetuximab.
Patients not taking Erbitux, distributed in the U.S. by Bristol-Myers Squibb and elsewhere by Merck and Co., also reported a higher quality of life.
All patients received the anticancer drugs Xeloda (capecitabine) from Roche, Eloxatin (oxaliplatin) from Sanofi-Aventis and Avastin (bevacizumab), sold by Genentech and Roche.
The team, led by Dr. Jolien Tol of the Radboud University Nijmegen Medical Center in the Netherlands, said the findings may have been due to a negative interaction between Erbitux and Avastin.
Avastin is known to raise blood pressure and patients who got four drugs did not have higher blood pressure, which the researchers said suggests Erbitux interferes with Avastin.
Both are monoclonal antibodies -- genetically engineered immune system proteins designed to starve tumors through two different mechanisms.
Other studies have shown that combining more drugs can help patients with cancer such as lung cancer. But not always, Dr. Robert Mayer of the Dana-Farber Cancer Institute in Boston wrote in a commentary. "As was observed in this situation, more is not always better," he wrote.
A spokesperson for ImClone said a comment was not immediately available.
Editing by Maggie Fox and Cynthia Osterman