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news.Myriad Genetics has reported that a presentation entitled: 'Extensive 5-FU Inter-Patient Pharmacokinetic Variability May Result in Suboptimal 5-FU Dosing of Metastatic and Adjuvant Colon Cancer Patients on FOLFOX Regimens,' was presented on January 24, 2010, at the Seventh Annual Gastrointestinal Cancers Symposium of the American Society of Clinical Oncology (ASCO) in Orlando, Florida.
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5-fluorouracil (5-FU) is used in many chemotherapy regimens, including FOLFOX (folinic acid, fluorouracil and oxaliplatin), FOLFOX6, and FOLFIRI (folinic acid, fluorouracil and irinotecan), and is used extensively in the treatment of colorectal, metastatic breast, and head and neck cancers.
The study investigated the chemotherapic dosing of 150 colon cancer patients in the US, including 102 patients who received FOLFOX6 and 48 patients who received FOLFOX6 plus Avastin. The results showed that when 5-FU is administered in combination with oxaliplatin according to current standard-of-care body surface area (BSA) dosing, 81.3% of the colon cancer patients had 5-FU exposure levels outside the optimal therapeutic range (Gamelin, et al, Journal of Clinical Oncology).
Additionally, 28.7% of the patients showed elevated exposure to the drug, from too high of a dose of 5-FU and resulting in increased risk of toxicity, including diarrhea, oral mucositis, and hand and foot syndrome, and 52.6% of the patients exhibited a suboptimal 5-FU exposure, receiving too little drug and potentially resulting in the inadequate treatment of their cancer.
Studies conducted during the last two decades show that there is tremendous pharmacokinetic variability in the way that patients metabolize 5-FU, with as much as a 30-fold difference in clearance of and resulting exposure to 5-FU during the course of treatment. Colon cancer patients in this US-based study also exhibited substantial variability in their drug exposure as determined by OnDose. A consequence of this variability among patients is the difficultly for physicians using conventional BSA dosing methods to strike an optimum balance between achieving maximum efficacy in treating the cancer, and, at the same time, avoiding serious toxicity in a particular patient.
Gregory Critchfield, president of Myriad Genetic Laboratories, said: “This study confirmed previous research that a majority of colon cancer patients do not receive an appropriate dose of 5-FU. We believe that our OnDose diagnostic test, which accurately measures a patient’s exposure to 5-FU, will save lives and improve the quality of life for patients with colon cancer.”