Treatment responses and disease dynamics in patients with untreated metastatic colorectal cancer receiving bevacizumab-based sequential versus combination chemotherapy: Analysis of a phase 3 trial (AIO KRK0110, XELAVIRI study).
Authors: Annika Kurreck, Volker Heinemann, Ludwig Fischer von Weikersthal, Thomas Decker, Florian Kaiser, Jens Uhlig, Michael Schenk, Jens Freiberg-Richter, Bettina Peuser, Claudio Denzlinger, Ullrich Graeven, Kathrin Heinrich, Swantje Held, Arndt Stahler, Annabel Helga Sophie Alig, Ivan Jelas, Jobst C. von Einem, Sebastian Stintzing, Clemens Giessen-Jung, Dominik Paul Modest
Journal: Journal of Clinical Oncology (2021)

3571 Background: Early response parameters such as early tumor shrinkage (ETS), depth of response (DpR), and time to DpR represent exploratory endpoints that may serve as early efficacy endpoints and potential predictors of long-term outcome. We analyzed the association of these endpoints with bevacizumab-based sequential (initial fluoropyrimidines) versus combination (initial fluoropyrimidines plus irinotecan) chemotherapy within a randomized phase III trial. Methods: DpR (change from baseline to smallest tumor diameter), ETS (≥20% reduction in tumor diameter at first reassessment), and time to DpR (study randomization to DpR-image) were analyzed in the XELAVIRI-trial. Moreover, progression-free survival (PFS) and overall survival (OS) were evaluated with ETS as stratification parameter (ETS vs. no ETS) according to treatment arm, molecular subgroup, and sex. Results: 370 patients were available for analysis of early treatment response parameters. A higher rate of ETS (60.9% vs. 43.5%; p = 0.001) and significantly greater DpR (-40.0% vs. -24.7%; p &lt; 0.001) were observed in the initial combination compared to the sequential therapy arm, respectively. The improvement of ETS and DpR was pronounced in the subpopulation of RAS/ BRAF wildtype patients. Male in contrast to female patients significantly benefitted from initial combination treatment in terms of median DpR (male: -40.0% vs. -22.2%; p &lt; 0.001; female: -34.0% vs. -24.4%; p = 0.13) and rate of ETS (male: 64.8% vs. 40.2%; p &lt; 0.001; female: 52.5% vs. 49.3%; p = 0.73). Achievement of ETS correlated with improved survival irrespective of treatment arm (PFS: p &lt; 0.001; OS: p = 0.012) and molecular subgroup (PFS: p &lt; 0.001; OS: p &lt; 0.001). Whereas the survival benefit in male patients achieving ETS was statistically significant (PFS: p &lt; 0.001, HR 0.532 (0.409-0.692); OS: p &lt; 0.001, HR 0.574 (0.437-0.756)), there were no significant differences in PFS (p = 0.107) and OS (p = 0.965) of female patients depending on ETS. Conclusions: In the XELAVIRI trial, initial irinotecan-based combination therapy with bevacizumab improves ETS and DpR in mCRC patients. Improvement in early response parameters appears pronounced in patients with RAS/ BRAF wildtype tumors suggesting a high sensitivity to irinotecan-based treatment. ETS was predictive of PFS and OS regardless of treatment arm. This finding was rather driven by male than female patients, potentially indicating that ETS might be less predictive of long-term outcome in an elderly, female population.