Zhibin Huang, Nina A. Mayr, Simon S. Lo, John C. Grecula, William T.C. Yuh, and Jian Z. Wang
DCE-MRI, Cervical Cancer, Radiation Therapy, At-risk Voxels
Purpose: In this study, a threshold value of signal intensity (SI=2.1) was used to characterize the number of low DCE voxels which is potentially related to treatment failure. Our goal was to instigate predictive power of at risk voxels in predicting treatment outcome during radiation therapy for cervical cancer. Methods and Materials: Data of 3D volumetric tumor regression and tumor perfusion from dynamic contrast enhanced MRI (DCE-MRI) from 104 patients with Stage IB2–IVB cervical cancer were analyzed. Three sequential MRI scans were performed pre-RT, every 2–2.5 weeks during RT. Based on the signal intensity (SI) curves of the DCE-MRI, the parameter of the number of the low-DCE tumor voxels was obtained for individual patients. Using the ROC analysis on this parameter, subsequentially the threshold values of the number of low DCE voxels were determined. Kaplan-Meier survival curves were performed to evaluate the predictive power of this parameter in predicting the treatment outcome. Results: It has been found that the 6-year actuarial local control rate and survival rate in the patient group with a low number of low DCE voxels (<304) were 90.9% and 79.5%, compared with 75% and 59.6% in the patient group with a high number of low DCE voxels (>304) for the MRI study #1. The 6-year actuarial local control rate and survival rate in the patient group with a low number of low DCE voxels (<224) were 94.9% and 83.1% compared with 59.5% and 46.5% in the patient group with a high number of low DCE voxels (>224) for the MRI study #2. The 6-year actuarial local control rate and survival rate in the patient group with a low number of low DCE voxels (<123) were 95.9% and 79.6% compared with 59.5% and 48.8% in the patient group with a high number of low DCE voxels (>123) for the MRI study #3. Conclusion: The number of at-risk voxels can be used as an important prognostic factor for outcome and help understand tumor heterogeneity of response to radiation therapy. DCE-MRI kinetics would be very useful as a tool in selecting patients and designing fields for adaptive radiation therapy.
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