Bulletin du cancer
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Treatments of advanced colorectal cancer progressing after a 5FU based chemotherapy have not been extensively studied. However, 5FU in continuous infusion, L-OHP alone or in combination with 5FU and CPT11 have proved their efficacy in terms of tumor growth control and symptomatic effect. Irinotecan only has been evaluated prospectively in phase III studies. ⋯ Both treatments were equally well tolerated. These two randomized studies have proved the efficacy of irinotecan as second line chemotherapy for colorectal cancers progressing under 5FU. Combination of irinotecan to 5FU and/or L-OHP have now to be evaluated in this situation.
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Irinotecan (CPT11), a topoisomerase I inhibitor, is a new cytotoxic agent with a broad spectrum of clinical activity. Two main schedules have been studied and produce similar activity and side-effects: the "european" one--350 mg/m2 every 21 days-, and the "japanese-north american" one where CPT11 is given at a weekly dose of 100-120 mg/m2 for 4 consecutive weeks followed by a 2 week rest period. Activity was initially characterized in advanced colorectal cancers; response rates, disease free-survival and overall survival were 11%, 7-10 months and 8-11 months in patients failing fluoropyrimidine based chemotherapy--statistically improved as compared to best supportive care and infusional fluorouracil-, and 20-30% in patients not previously treated. ⋯ Irinotecan can be combined to fluoropyrimidines, raltitrexed, cisplatin, carboplatin and oxaliplatin, to gemcitabine, etoposide, vinorelbine and taxanes with flexible schedules (weekly, every 2 weeks, every 21 days. Most of these combinations have an additive or supra additive activity. Its mechanism of action, the spectrum of activity and the acceptable risk-benefit ratio point to irinorecan as a major advance in the field of cytotoxic anticancer therapy.
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Review
[Irinotecan: various administration schedules, study of drug combinations, phase I experience].
Irinotecan (CPT11) is a synthetic camptothecin-derived DNA topoisomerase I inhibitor. Based on phase I clinical trials, several schedules have been recommended for phase I studies including 350 mg/m2 every 3 weeks in Europe, 125 mg/m2 for 4 weeks every 6 weeks in the USA, and 100 mg/m2 weekly or delayed until recovery in case of grade > 2 toxicity in Japan. The principal dose-limiting toxicities in those schedules are neutropenia and delayed diarrhea. ⋯ Those variations may be related to modifications in the hepatic metabolism of the drug that may occur in patients with hepatic dysfunction and/or in patients with concomitant medications. The understanding of the individual metabolism of the drug would help to determine individual dose adaptation. Based on synergistic preclinical interaction with several drugs, combinations of irinotecan with other cytotoxic drugs such as thymidylate synthethase inhibitors and platinum salts are currently investigated in phase I-II studies.
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As a single agent, irinotecan has demonstrated efficacy in metastatic 5FU resistant colorectal metastatic cancer. Chemotherapy with fluorouracil (5FU) plus leucovorin remains a standard in the treatment of patients with metastatic colorectal cancer. It seemed logical to test the combination of this reference treatment and the new agent. ⋯ The combinations of irinotecan and mitomycin C or oxaliplatin have given very good results with high objective response rates and good tolerance. Irinotecan plays now an important part in the treatment of metastatic colorectal cancer. This part becomes larger due to the results of the combination trials already presented which have shown strong efficacy and good tolerance.
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Irinotecan or CPT11 is a topoisomerase 1 inhibitor. The European and American regimens of irinotecan in monotherapy are different: respectively 350 mg/m2 i.v. every 3 weeks and 125 mg/m2 i.v. weekly (4 weeks out of 6). In a large phase 2 programme an important activity has been shown in metastatic colorectal cancer. ⋯ This interesting activity was the basis for the phase 3 studies that have positioned irinotecan as the standard treatment in 5FU resistant colorectal cancer. The response rate in first line treatment of colorectal cancer varies between 18% and 32%. The main side effects are neutropenia and delayed diarrhea.