Dosing considerations for capecitabine-irinotecan regimens in the treatment of metastatic and/or locally advanced colorectal cancer.

Capecitabine (Xeloda®, Roche Laboratories Inc., Nutley, NJ) is an orally administered fluoropyrimidine carbamate that serves as a prodrug of 5-fluorouracil (5-FU), an integral component of chemotherapy (CT) regimens for metastatic colorectal cancer (mCRC). As the drug is orally administered, capecitabine permits greater convenience and flexibility in dosing by eliminating the need for continuous infusion and its potential complications. In phase 3 trials, capecitabine has been used as an alternative to 5-FU, both as a monotherapy and in combination with agents such as oxaliplatin (as XELOX), with good efficacy and tolerability. Combination therapy with capecitabine and irinotecan (XELIRI), however, has produced more variable results, with some dose combinations and schedules resulting in excessive and/or unexplained treatment-related toxicity. Recent initiatives using lower doses of capecitabine and irinotecan, as well as alternative dosing schedules, have resulted in more favorable outcomes (efficacy and tolerability), even in combination with targeted-agents such as bevacizumab. Dose reduction in elderly populations and in those with moderate renal impairment also appears to be important for minimizing toxicity with XELIRI regimens. Although additional phase 3 studies are needed, XELIRI may be an effective base CT regimen, allowing a greater number of treatment options for tumor control in patients with mCRC.