DPD Ultra-Rapid Metabolizer Status and Efficacy of 5-Fluorouracil Treatment: A Real-World Study

Background

Anticancer drug 5FU is extensively metabolized by dihydropyrimidine dehydrogenase (DPD), an enzyme with high interindividual variability. Poor metabolizer (PM, i.e., DPD deficient) patients are at risk of life-threatening toxicities. Whether ultra-rapid metabolizer (UM) status could conversely compromise 5FU efficacy remains to be investigated.

Methods

In this real-world study, 352 adult patients treated with a 5FU-containing regimen were screened. Patients were classified as normal (extensive metabolizer, EM), PM, or UM on DPD function based upon baseline plasma uracil monitoring. The impact of DPD status on efficacy and safety endpoints was investigated.

Results

Patients were categorized on DPD as UM (11.9%), EM (75.9%), and PM (12.2%). The response rate was 54.5%, with median PFS and OS of 13.9 and 19 months, respectively. PM patients were treated with an average 13% lower 5FU starting dose. There was no statistical difference in efficacy between UM and other patients. Severe toxicities were observed in less than 5% of patients, an incidence significantly lower than commonly reported with 5FU-containing regimen and was comparable between UM, EM, and PM patients. Our observations suggest that UM status is not associated with the lack of efficacy of 5FU. In addition, upfront DPD testing with adaptive dosing helps to reduce the incidence of severe toxicities, as PM patients on reduced doses did not have more severe toxicities than other patients treated with standard doses, while exhibiting similar efficacy in terms of response rate and survival.

Conclusion

When upfront DPD screening with adaptive dosing is performed, no difference is observed between UM, EM, and PM patients in terms of efficacy and safety.

Trial Registration

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