The impact of single-hetero UGT1A1 on clinical outcomes of irinotecan monotherapy in gastric cancer after fluoropyrimidine, platinum, and taxanes: Multicenter retrospective study.

Abstract

296 Background: Japanese gastric cancer treatment guidelines (5th edition) recommend irinotecan (IRI) after fluoropyrimidine, platinum and taxanes as a third line chemotherapy. We previously reported that patients with UGT1A1 single heterozygous (SH) had significantly high frequency of severe hematological adverse events (AEs) compared to patients with UGT1A1 wild type (WT) in IRI monotherapy for advanced gastric cancer (AGC). However, it remains unclear that UGT1A1 SH affect efficacy and safety of IRI after fluoropyrimidine, platinum and taxanes compared to WT as a salvage line. Methods: We retrospectively analyzed the clinical data of patients who received IRI monotherapy after fluoropyrimidine, platinum and taxanes in the multi-institutional retrospective study. From January 2010 to December 2017, 69 eligible patients were registered from 8 centers in Japan. Results: Forty one patients with UGT1A1 WT and 28 patients with UGT1A1 SH were included in this study. In WT/SH patients, performance status 0/1/≥2 was 12/25/4 and 5/17/6, treatment line 3rd/4th or later was 33/8 and 26/2, HER2 status positive/negative was 12/29 and 5/23, respectively. In WT/SH patients, rate of initial dose reduction was 22 and 28% (P = 0.363), median relative dose intensity (RDI) was 82% and 80% (P = 0.309). Of 88 patients who have measurable lesions, the overall response rate (ORR) was 5.7% and 4.2% (P = 1.000), disease control rate (DCR) was 54% and 38% (P = 0.289). Median progression free survival was 3.2 and 2.1 months (HR 0.607, P = 0.058) and median overall survival from initial day of IRI monotherapy was 10.0 and 7.0 months (HR 0.618 P = 0.086). In WT/SH patients, severe hematological AEs (≥G3) were observed more frequently in patients with UGT1A1 SH (WT: 43% and SH: 68%, P = 0.050), although frequency of severe non-hematological AEs (≥G3) were not significantly different in both groups (13% and 25%, P = 0.211). Conclusions: Compared to UGT1A1 WT, UGT1A1 SH status may be associated with poor efficacy and be a risk factor of higher frequency of severe hematological AEs.