Apparent diffusion coefficient: Potential imaging biomarker for prediction and early detection of response to chemotherapy in hepatic metastases

Purpose: To evaluate the ability of the apparent diffusion coefficient (ADC) to help predict response to chemotherapy in patients with colorectal and gastric hepatic metastases. Materials and Methods: Institutional review board approval was obtained; all patients provided informed consent. Standard magnetic resonance (MR) imaging and diffusion-weighted (DW) MR imaging were performed before and 3, 7, and 42 days after initiating chemotherapy for 87 hepatic metastases in 23 colorectal and gastric cancer patients (16 men, seven women; mean age, 55.7 years; range, 33-71 years). Lesions were classified as either responding or nonresponding, according to changes in size at the end of therapy. Linear mixed-effects modeling was applied to analyze change in ADCs and size following treatment. The Pearson correlation test was calculated between those ADC parameters and tumor response. Results: Thirty-eight responding and 49 nonresponding metastatic lesions were evaluated. Pretherapy mean ADCs in responding lesions were significantly lower than those of nonresponding lesions (P = .003). An early increase in ADCs (on day 3 or 7) was observed in responding lesions but not in nonresponding lesions (P = .002). Weak but significant correlations were found between final tumor size reduction and both pretreatment ADCs (P < .006) and early ADC changes (day 3, P = .004; day 7, P < .001). Conclusion: ADC seems to be a promising tool for helping predict and monitor the early response to chemotherapy of hepatic metastases from colorectal and gastric carcinomas. (C) RSNA, 2008.