Raltitrexed (Tomudex): an alternative choice in patients intolerant to 5-fluorouracil.

Raltitrexed (Tomudex), a classical folate antagonist, is a selective inhibitor of thymidylate synthase (TS). It has significant single-agent activity in metastatic colorectal cancer. Severe life-threatening toxicity related to the administration of 5-fluorouracil and leucovorin is described in two patients, both of whom were not deficient in dihydropyrimidine dehydrogenase. Raltitrexed was administered to both patients with clinically acceptable side effects and allowed a TS inhibitor to be administered as part of an adjuvant program.