Choi criteria can provide a window into anti-tumor activity when traditional methods fail to reveal response outcomes that are demonstrated in improved patient outcomes. It is not uncommon that targeted therapy and precision medicine do not alter tumor size but do alter the appearance of tumors. Traditional response criteria such as RECIST 1.1 focus on changes in the size of lesions to evaluate a response outcome. Choi criteria focuses on changes in tumor enhancement (density) on CT as an indicator of response that may be observed with or without evidence of size changes in lesions on imaging. Here we discuss how Choi criteria may provide another option in evaluating efficacy in clinical trials.