Relationships Between Kohne Category/Baseline Tumor Load and Early Tumor Shrinkage, Depth of Response, and Outcomes in Metastatic Colorectal Cancer

Abstract

In metastatic colorectal cancer, there are few data on associations between early tumor shrinkage (ETS), depth of response (DpR), and patient characteristics. We assessed ETS and DpR by baseline Kohne category and tumor load. High-risk patients or those with BRAF mutations have lower chances of achieving an ETS of 30% or greater or a high DpR. An ETS of 30% or greater and a high DpR were associated with prolonged survival. Baseline tumor load was not linked with achieving an ETS of 30% or greater or a high DpR.Background: In metastatic colorectal cancer (mCRC), there are limited data on associations between early tumor shrinkage (ETS), depth of response (DpR), and patient characteristics. Methods: Data from patients with RAS wildtype mCRC who had participated in the PRIME (NCT00364013) and PEAK (NCT00819780) studies were analyzed retrospectively. ETS and DpR were assessed by baseline Kohne category/BRAF status (PRIME) and baseline tumor load (pooled PRIME and PEAK). Results: Analysis populations included 436 to 665 patients. Patients' chances of achieving ETS of 30% or greater were 63.8%, 50.4%, and 41.9% in the low-, medium-, and high-risk Kohne categories, and 21.7% in those with BRAF mutations. Corresponding percentages for the highest DpR classification (71%-100%) were 47.7% (low risk), 23.6% (medium risk), 10.0% (high risk), and 4.2% (BRAF mutant). No clear relationship was observed between baseline tumor load and ETS or DpR. An ETS of 30% or greater and higher DpR values were associated with statistically significant prolongation of median progression-free survival and overall survival. Conclusion: Patients with mCRC categorized at baseline by the Kohne criteria as high risk or with BRAF mutations have lower chances of achieving an ETS of 30% or greater or a high DpR. Baseline tumor load was not predictive of ETS or DpR. Favorable ETS or DpR is associated with improved progression-free and overall survival.