CHICAGO--With an overall response rate of only 2.8% to drugs tested on more than 1,200 colorectal cancer patients over the last 20 years, new drug development has given gastrointestinal oncologists little to be enthusiastic about.
This picture has changed markedly in the last year, however, with FDA approval of CPT-11 or irinotecan(Drug information on irinotecan) (Camptosar), a drug active against refractory colorectal cancer, and early clinical trial results of three other drugs which could someday supplant fluorouracil(Drug information on fluorouracil) in the treatment of primary colorectal cancer, said Mace Rothenberg, MD, at the 9th meeting of the Atlanta-based Network for Oncology Communication & Research.
CPT-11 was approved based on overall response rates of 13% in three phase II clinical trials of patients whose colorectal disease had progressed after one fluorouracil-based regimen. More important, Dr. Rothenberg said, the drug stabilized colorectal cancer in an additional 50% of patients.
"We were all trained to believe that stable disease indicated no benefit. I disagree with that position. With this drug, we see a consistently high percentage of patients whose disease stabilized for a median period of 6 months, a meaningful period of time before developing progression," said Dr. Rothenberg, associate professor of medicine, University of Texas Health Science Center, San Antonio.
Tomudex Results Pending
Among the drugs that have potential as front-line therapies for colorectal cancer, tomudex (Merck & Co., Inc.) has progressed the furthest in clinical testing, Dr. Rothenberg said. In phase II trials in Europe and Australia, the drug achieved an overall response rate of 26% and stabilized disease in an additional 49% of 177 newly diagnosed patients with colorectal cancer.
The drug also appeared to be equivalent to fluorouracil plus low-dose leuco-vorin in a European phase III trial involving 439 newly diagnosed colorectal cancer patients.