A phase I/II study of biweekly XELIRI plus bevacizumab for patients with metastatic colorectal cancer as second-line chemotherapy (BIXER study): Reports of phase I part and interim analysis of phase II part.

Abstract

643 Background: Capecitabine is an oral fluoropyrimidine prodrug, which is converted to fluorouracil (5-FU) predominantly in the tumor cells. In Japan, capecitabine is mainly used in combination with oxaliplatin (XELOX) in treatment for metastatic colorectal cancer (mCRC) since its approval in 2009. The results of capecitabine plus Irinotecan (CPT) (XELIRI) with or without bevacizumab (BV) in EU or US patients were previously reported, but not in Japanese. Thus, we conducted this study to assess the safety and efficacy of XELIRI plus BV in Japanese patients with mCRC. Methods: Patients with prior chemotherapy including oxaliplatin and BV for mCRC, wild or hetero type of UGT1A1 *6*28 were eligible for this study. This was a phase I study composed of two steps, and dose limiting toxicity (DLT) was assessed during the first treatment cycle. Treatment comprised capecitabine 1,000 mg/m2 twice daily from the evening of day 1 to the morning of day 8, intravenous CPT 180 mg/m2 on day 1, and BV 5mg/kg on day 1 every two weeks. To evaluate the initial safety, 3-6 patients received XELIRI+BV (CPT 150mg/m2) in step 1, and 6 patients received XELIRI+BV (CPT 180mg/m2) in step 2. If DLT occurred in 1 patient in step1, 3 patients would be newly added to step 1, and if in none of 3 or 1-2 of 6 patients, the step 2 would be started. If DLT occurred in less than or equal to 2 of 6 patients in step 2, phase II study would be proceeded, and if In more than 2 of 6 patients, phase II would be conducted at the recommended dose of step 1. Results: In step 1 and 2 of phase I, initial safety of 9 patients was confirmed without occurrence of DLT. Adverse events observed in step 1 and 2 were: neutropenia in 2 and 1; anorexia in 1 and 1; diarrhea in 1 and 1; stomatitis in 1 and 1; alanine or aspartate aminotransferase increased in 1 and 3, respectively. There was no grade 3 or greater adverse events. Conclusions: In mCRC patients with wild or hetero of UGT1A1*6*28 genotype, safety of biweekly XELIRI+BV was confirmed and recommended dose of CPT-11 was determined as 180mg/m2. Interim analysis of safety of phase II part will be reported at the meeting.