[Absence of cross resistance between an irinotecan plus cisplatin combination and raltitrexed (ZD1694) in two patients with advanced colorectal cancer].

Two patients with advanced colorectal cancer were consecutively administered two different chemotherapeutic regimens. The first patient showed an initial response to combination treatment with irinotecan plus cisplatin, but then progressed. He subsequently responded to treatment with a novel thymidylate synthase (TS) inhibitor, raltitrexed. The second patient, who progressed after exhibiting a response to raltitrexed, subsequently responded to irinotecan/cisplatin combination therapy. In conclusion, no clinical cross resistance between the regimens of irinotecan/cisplatin combination therapy and raltitrexed was observed in these patients with advanced colorectal cancer.