UGT1As polymorphisms predict toxicity in colorectal cancer patients treated with different recommended doses of irinotecan oriented by UGT1A1*28 polymorphism based on previous phase I study

Abstract

14511 Background: We have presented at 2006 ASCO annual meeting about a genetic UGT1A1 polymorphism oriented phase (P) I study of Irinotecan and 5’-DFUR for metastatic colorectal cancer (MCRC) to determine the maximum tolerated dose (MTD) and the recommend doses (RD) for each UGT1A1 *1/*1 and *1/*28 genotypes. The RD of biweekly Irinotecan administration was 150 mg/m2 for patients (pts) with wild *1/*1 genotype and 70 mg/m2 of Irinotecan for mutated *1/*28. Now we are carrying out a *28 oriented P II study based on this RD. Here we report the profiles of toxicities in the P II study of irinotecan and 5’-DFUR to analyze other kinds of UGT1As polymorphisms in relation to irinotecan toxicities. Patients & Methods: Eligibility criteria were as follows; histologically proven CRC with unresectable metastatic lesions, PS 0–1, age<76, adequate organ functions, and written informed consent. Twenty one pts with wild type genotype and 9 pts with mutated genotype were enrolled. Irinotecan was infused 150 mg/m2 for pts with *1/*1 genotype and 70 mg/m2 for *1/*28. Hematological and non-hematological toxicities were graded, and UGT1As polymorphisms (UGT1A1*6 and *7, UGT1A7*1*2*3*4, UGT1A9*22) were analyzed. Results: Grade (G)3 & 4 toxicities were observed in 6 of 22 (27%) wild type pts and in 3 of 9 (33%) mutated pts, and in 9 of 31 (29%) all pts. There was no significant difference on the profiles of toxicities between the pts with wild genotype and mutated genotype, irrespective of the difference of the quantity of irinotecan. So, the RD was thought to be adequate. In pts with UGT1A1*6 allele, G3 & 4 toxicities were observed 6/11 (55%), on the other hand 3/20 (15%) in pts without *6 allele (p=0.038). G3 & 4 toxicities were also more frequent in pts with UGT1A7*3 alleles than pts without *3 allele (p<0.10). Conclusions: The profiles of toxicities of pts with *1/*1 or *1/*28 genotypes were similar irrespective of the difference of the quantity of irinotecan. The result indicated that the RD of latest PI for each group was adequate, and this P II study is suitable to analyze other kinds of polymorphisms that have correlation to irinotecan toxicities. UGT1A1*6 and UGT1A7*3 allele will be a novel predictor for toxicity of irinotecan. No significant financial relationships to disclose.