Phase IB/II Study of Second-Line Therapy with Panitumumab, Irinotecan, and Everolimus (PIE) in KRAS Wild-Type Metastatic Colorectal Cancer.

Abstract

Background: Inhibition of mTOR in addition to EGFR may overcome resistance to EGFR inhibitors in metastatic colorectal cancer (mCRC). This phase Ib/II study evaluated the safety and efficacy of the combination of irinotecan, panitumumab, and everolimus.Method: Patients with KRAS exon 2 wild-type (WT) mCRC following failure of fluoropyrimidine-based therapy received i.v. irinotecan and panitumumab every 2 weeks, and everolimus orally throughout a 14-day cycle. The primary endpoint of the phase II study was response rate (RR). Secondary survival outcomes were calculated using the Kaplan-Meier method, and results were analyzed as intention to treat. A preplanned exploratory biomarker analysis was performed.Results: Forty-nine patients were enrolled. Dose level 1 (irinotecan 200 mg/m2, panitumumab 6 mg/kg, and everolimus 5 mg alternate day) was declared the MTD with no dose-limiting toxicities in six patients. Forty patients were treated at dose level 1: median age, 60 years (37-76); 65% male; 45% and 52.5%, respectively, with Eastern Cooperative Oncology Group values of 0/1. Median dose intensity was 85%. Grade 3 toxicities were diarrhea (23%), mucositis (18%), rash (13%), fatigue (8%), dehydration (5%), neutropenia (20%), febrile neutropenia (8%), hypomagnesemia (20%), and hypokalemia (8%). Grade 4 toxicities were hypomagnesemia (5%) and neutropenia (3%). RR was 48%, and stable disease was 43%. Median progression-free survival (PFS) was 5.6 months, and median overall survival (OS) was 10.8 months. Twenty-five patients were RAS/RAF WT and had an RR of 60%, median PFS of 6.4 months, and OS of 11.8 months.Conclusions: The toxicity of the panitumumab, irinotecan, and everolimus regimen is as expected and manageable. The RR of 60% in all RAS/RAF WT supports further study of this combination. Clin Cancer Res; 1-7. ©2018 AACR.