The importance of early tumor shrinkage and deepness of response in assessing the efficacy of systemic anticancer treatment with metastatic colorectal cancer

Abstract

The efficacy of anticancer therapy is regularly evaluated using the following indicators - objective response rate, progression free survival and overall survival. The change in the tumor burden extent is assessed by the cumulative change in the size of target tumor lesions using imaging methods where WHO and RECIST criteria are most frequently used. The main problem of these criteria is that they use different definitions of response rate evaluation. Generally, existing results of these evaluations do not confirm a direct correlation between the objective response rate and survival (progression free survival or overall survival). Another problem of these methods is that the results of the assessment do not correlate with the bio-logical activity of tumor growth, since it is a static evaluation of clinical status. This review article provides an overview of results related to new possibilities for evaluating the efficacy of anticancer therapy using the concept of depth of response and the concept of early tumor shrinkage in patients with metastatic colorectal cancer. The results of numerous posthoc and exploratory analyses of clinical studies consistently suggest that early tumor shrinkage and depth of response are important variables in assessing the efficacy of systemic anticancer treatment.