A UGT1A1 genotype-directed phase II toxicity and efficacy-finding study of irinotecan combined with S-1 as first-line treatment in advanced gastric cancer.

Abstract

TPS4154 Background: The best chemotherapy regimen for advanced gastric cancer (AGC) is uncertain, but promising findings have been reported with Irinotecan (IRI) plus S-1. However, IRI can induce severe neutropenia or diarrhea associated with homozygosity of the UGT1A1*28 or UGT1A1*6 alleles. This trial was designed to compare the toxicity and efficacy on different doses of IRI combined with S-1 according to UGT1A1 genotype as first-line chemotherapy in AGC in Chinese patients. Methods: Previously untreated patients with histologically proven gastric or gastroesophageal junction adenocarcinoma, aged between 18 and 75 years with ECOG performance status 0-2 were classified according to UGT1A1 genotype: wild-type (none of *28 or *6 allele); heterozygous (only one of *28 or *6 allele); or homozygous (*28/*28, *6/*6, or double heterozygous for *28 and *6). Patients were randomized (1:1) to receive either low or high dose of IRI given i.v. (90 min) on day 1 in each genotype group. The low and high dose of IRI were 80mg/m2 and 200 mg/m2 in the wild-type group, 80 mg/m2 and 150 mg/m2 in the heterozygous group, 40 mg/m2 and 80 mg/m2 in the homozygous group. S-1 was administered orally at a dose level set on the basis of the body surface area (BSA): 40 (BSA<1.25 m2), 50 (BSA≥1.25 to<1.5 m2 ) or 60 mg (BSA≥1.5 m2) twice a day on day1-7. Courses were repeated every 2 weeks, unless disease progression, unacceptable toxicity or patient refusal. The primary endpoint was to explore the safety and efficacy on different doses of IRI combined with S-1 according to UGT1A1 polymorphism. Based on the frequency of UGT1A1*28 and UGT1A1*6 gene polymorphism in Asian gastrointestinal cancer patients, the chi-square test and fisher exact test were used to evaluate the planned sample size which is 100 in total: 40 for the wild-type, 40 for the heterozygous and 20 for the homozygous group. Until now, 8 patients have been enrolled. Clinical trial information: ChiCTR-OCH-12002472.