Diffusion-weighted Magnetic Resonance Imaging Allows Monitoring of Anticancer Treatment Effects in Patients with Soft-tissue Sarcomas

Purpose: To determine if diffusion-weighted imaging (DWI) can be used as a surrogate marker of tumor response to anticancer therapy in patients with soft-tissue sarcomas.

Materials And Methods: Magnetic resonance imaging (MRI) including echo-planar DWI sequences was performed prospectively in 23 consecutive patients with soft-tissue sarcomas before and after initiation of regional or systemic chemotherapy. The mean interval between initial and follow-up MRI was 56.9 +/- 23.2 days. Tumor volumes were determined by manual segmentation of tumor borders on contrast-enhanced T1-weighted images. The apparent diffusion coefficient (ADC) was calculated from corresponding sections of ADC maps on initial and follow-up DWI. Subsequently, changes in tumor volumes and ADC were correlated using the Pearson correlation coefficient.

Results: A high degree of correlation was found when changes in tumor volumes and ADC values were compared (r = -0.925, P < 0.0001), regardless of the effectiveness of anticancer therapy expressed as changes of tumor volume.

Conclusion: DWI can be used as a supplement to morphologic imaging for the evaluation of tumor response to anticancer therapy in patients with soft-tissue sarcomas. As cellular changes are expected to precede morphologic changes in treated tumors, DWI performed at an early stage of fractionated therapy may provide unique prognostic information of its effectiveness.