Researchers identify biomarker to predict response of colon cancer patients to chemotherapy regimen

06/01/04

Researchers at Fox Chase Cancer Center have identified a biomarker that can predict how well individual colon cancer patients will respond to a common chemotherapy regimen. This finding is a significant step forward in the goal of personalizing cancer treatment. Medical oncologist Neal J. Meropol, M.D., director of the gastrointestinal cancer program at Fox Chase, presented the study today in New Orleans at the 40th Annual Meeting of the American Society of Clinical Oncology.

The study involves an enzyme that is important in activating capecitabine. Capecitabine is a commonly used oral chemotherapy drug that is converted into its active form by the enzyme thymidine phosphorylase (TP). TP is found in some, but not all, cancers. Capecitabine (marketed by Roche under the name Xeloda) in combination with irinotecan ( marketed by Pfizer under the name Camptosar) is a chemotherapy regimen being developed to treat advanced colon cancer patients.

Meropol's study was designed to see if a correlation exists between how well a patient with metastatic colorectal cancer responds to chemotherapy with capecitabine plus irinotecan, and whether or not the amount of TP in the tumor predicted success with therapy. The study included 67 patients, ranging in age from 40 to 81, who had received no prior chemotherapy for their metastatic disease.

Patients whose tumors had the enzyme TP, believed to be needed in the final step to convert capecitabine to its active form of 5-FU (fluorouracil), had a significantly higher response rate to the chemotherapy regimen. Specifically, the response rate for patients whose primary tumors tested positive for TP was 65 percent compared to 27 percent in patients whose primary tumors tested negative for TP. Among patients whose metastatic tumors expressed TP, the response rate was 61 percent compared to 14 percent in patients without TP in metastases.

"These data suggest that TP expression may be useful as a marker in predicting a positive response to chemotherapy with capecitabine plus irinotecan for colorectal cancer patients," Meropol said. "With that information, we can begin personalizing treatment. If we know the enzyme is present to activate the drug, we may be able to identify those patients who should receive capecitabine."

Source: Eurekalert & others

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