Irinotecan Plus Raltitrexed as Second-line Treatment in Advanced Colorectal Cancer Patients

The standard initial treatment for patients with advanced colorectal cancer (ACC) not amenable for surgical resection is palliative 5-fluorouracil (5-FU)-based chemotherapy. However, response rates are low and prognosis remains poor, with median survival times about one year. Until recently, second-line therapy options were limited. Irinotecan is a semisynthetic camptothecin derivate that acts as a DNA-topoisomerase-1 inhibitor,its most frequent toxic effects are diarrhea, neutropenia and cholinergic syndrome. Raltitrexed is a quinazoline folate-based specific thymidylate synthase inhibitor, its clinical activity in this setting is similar to that of modulated 5-FU regimens but with a better toxicity profile (mainly asthenia and increased serum transaminase levels). There seems to be no cross-resistance between 5-FU and raltitrexed. Irinotecan and raltitrexed have different toxicity profiles and modes of action. Both drugs are active as single agents and may be given as a short 3-weekly infusion, thus obviating complex schedules or the need for implantable venous access devices. Preclinical studies have demonstrated a pronounced sequence-dependent synergy between SN-38 (the active metabolite of irinotecan) and raltitrexed. It seems then interesting to explore the feasibility and therapeutic potential of this association. With this background, the investigators have performed this study to evaluate efficacy and safety of irinotecan plus raltitrexed as second-line treatment in advanced colorectal cancer patients.