Initial change in tumor size as an imaging surrogate of outcomes in patients with metastatic colorectal cancer (mCRC) treated with first-line irinotecan and 5-FU combination chemotherapy.

Abstract

3569 Background: Changes in tumor size using WHO RECIST-criteria have been extensively employed to monitor palliative chemotherapy and describe objective treatment response (OR). Few have questioned the fixed thresholds for response evaluation, particularly using RECIST and the relevance of an OR for patient prognosis is unclear. The aim was to determine whether the magnitude of change in tumor size at the first follow-up CT-examination after baseline examination (first change) correlates with outcome in patients with metastatic colorectal cancer (mCRC) treated with combination chemotherapy. Methods: The first change was retrospectively analyzed in a multicenter randomized phase III trial (Nordic VI, n=567) comparing first-line irinotecan with either bolus or infused 5-FU. Cox proportional hazards multiple regression model and Kaplan-Meier survival analyses after correction for guarantee-time bias were performed to evaluate correlations between first change, OR according to RECIST 1.0, progression-free su...