Magazine article Drug Topics

New Oncology Agent Treats Colorectal Cancer

Magazine article Drug Topics

New Oncology Agent Treats Colorectal Cancer

Article excerpt

The Food & Drug Administration appears to be keeping its promise to whisk oncology agents through the drug approval process. Camptosar (irinotecan HCI injection), manufactured by Pharmacia & Upjohn, is the fourth new oncology agent to be given the green light since the agency vowed back in March to step up the drug approval process for this class of drugs (see Drug Topics, April 22). Irinotecan is a topoisomerase 1 inhibitor and is indicated as second-line therapy in patients with metastatic colorectal cancer.

According to Leonard Saltz, M.D., member of the gastrointestinal oncology service, department of medicine at Memorial Sloan-Kettering Cancer Center, New York City, the excitement about irinotecan started in Japan. Researchers there reported a 27% response rate (defined as a greater than 50% reduction in tumor size) in patients with colorectal cancer, the vast majority of whom had already progressed through standard fluorouracilbased chemotherapy. A subsequent phase II trial conducted in the United States confirmed these results, with a 23% response rate in patients who had failed 5-FU therapy.

"That was very exciting, because this is a population of patients for whom chemotherapy doesn't usually work," said Saltz. He and his group studied the drug in a population that had received no prior chemotherapy and reported a 32% response rate.

Saltz said that in addition to the percentage of patients who had a 50% or greater reduction in tumor size, other clinical benefits were seen as well. For example, a large number of patients had tumor shrinkage up to 50%, some experienced improvement in their tumor-related pain and symptoms, performance status improved, and blood tests showed a decrease in levels of CEA, a marker of tumor extent.

"So the actual percentage numbers you see thrown around are smaller than the actual number of patients who derive clinical benefit," Saltz said.

Subsequent studies conducted by Pharmacia & Upjohn showed a 13% response rate, but Saltz indicated that because of the initial optimism about the drug, this study evaluated the drug in a population that had more advanced disease and was therefore less likely to respond. "Far more than those 13% of patients got clinical benefit," he said. …

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