Figure 2. Correlation Between Observation Period and Tumor Growth.

A, Percentage change in tumor diameter. B, Logarithmic index of volume change by length of observation period. Y₁ indicates tumor diameter in the screening examination (millimeters); Y₂, tumor diameter in the confirmatory examination (millimeters). There were no significant correlations between the observation period and either the percentage change of the tumor diameter (Pearson R = 0.098; 95% CI, –0.085 to 0.276) or the logarithmic index of volume change (Pearson R = 0.121; 95% CI, –0.062 to 0.297). The logarithmic index of volume change well reflects the percent change in tumor diameter. The tumor growth rate is not exponential.