KLK3 and leukemia: In addition to measuring total tumor volume via 2D or 3D imaging techniques and estimating viable tumor fraction from scan cross-sections—both of which we simulate here in our test scenarios—other choices of metrics could include testing for certain tumor antigens (such as prostate-specific antigen, or PSA, in prostate cancer [28]), measuring white blood cell counts for leukemia and other blood cancers, or checking for genetic biomarkers for use in a diagnostic setting.