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 (Camptosar), a drug active
against refractory colorectal cancer, and early clinical trial
results of three other drugs which could someday supplant 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.