Background: In Japan, CPT-11 is often used to treat unresectable gastric cancer in the second-line setting. However, evidence regarding benefit of second-line chemotherapy remains sparse, especially after failing S-1.
Methods: A phase II study to evaluate the efficacy and safety of weekly administration of CPT-11 at a dose of 100 mg/m(2) after failing a S-1-containing first-line treatment was planned with response rate as a primary end point. UGT1A1*6, *27, and *28 genotyping were performed in all cases, and those found to have either homozygous for *28, homozygous for *6, heterozygous for both *6 and *28, and heterozygous for *27 were rendered ineligible for the phase II trial.
Results: Two patients of homozygous for *28, two patients of homozygous for *6, and one patient of heterozygous for *27 were found among 39 recruited patients. The median number of courses delivered was 3 courses. The overall response rate was 15.4 % and disease control rate was 65.4 %. The median time to treatment failure was 87.5 days and median overall survival was 268 days. Twenty-two (73 %) of 30 valuable patients experienced protocol-specified skip of treatment and 8 (30 %) of patients could continue treatment with dose reduction. ≥G3 neutropenia was found in 30 % and ≥G3 anorexia and diarrhea were found in 23 and 17 %, respectively.
Conclusion: Weekly CPT-11 at 100 mg/m(2) showed moderate response among gastric cancer patients who were refractory to S-1, but the disease control rate seemed meaningful. Even after selection of patients by UGT1A1 polymorphism of *6, *27, and *28, severe toxic events could not be prevented completely.