Early Evaluation of Cancer Response by a New Functional Biomarker: Apparent Diffusion Coefficient

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The purpose of this article is to investigate whether apparent diffusion coefficient (ADC) might be used as a universal biomarker for response evaluation in different tumors. Twenty-one patients with lung cancer, 12 patients with esophageal cancer, 19 patients with liver metastases, 24 patients with gastric cancer, and 26 patients with rectal cancer were recruited to the study. Percentage changes in the ADC and changes in the size of responding and nonresponding lesions of different tumors after treatment were analyzed using repeated measures analysis of variance. There was no significant difference among the percentage ADC changes of different tumors (F = 1.57; p = 0.192). Clear differences were seen in the percentage ADC changes between responding and nonresponding tumors (F = 21.62; p < 0.001), which were significant at every time point after the start of treatment (early time point, F = 19.75 and p < 0.001; middle time point, F = 11.23 and p = 0.001; and later time point, F = 15.98 and p < 0.001). The percentage size changes after treatment between responding and nonresponding tumors were significantly different (F = 19.38; p < 0.001). However, at the early time point after treatment, the difference was not statistically significant (F = 0.02; p = 0.894). The ADC changes correlated with treatment response in five types of body tumor but were independent of the tumor's location. Early increases in ADC during treatment indicate good response to treatment. ADC change is a promising biomarker for detecting therapeutic responses at an early stage that could be widely used.