Purpose: There is need for imaging biomarkers to identify radiation resistant tumors and guide radiotherapy of cervical cancer. As such, MR-guided adaptive radiotherapy has the potential to provide improvements to the therapeutic ratio. Parameters derived from diffusion-weighted MRI (DW-MRI) are appealing quantitative biomarkers because DW-MRI does not require exogenous contrast agents, has relatively short scan time, and is ubiquitous across systems owing to its role in diagnosis. Important histologic properties that correlate with apparent diffusion coefficient (ADC) include tumor proliferation index, tumor grade, presence of necrosis, and post-therapy tumor cell apoptosis The purpose of this study was to evaluate cervical cancer ADC histograms prior to and following concurrent chemoradiotherapy (CCRT).
Methods: Five cervical cancer patients who underwent a 4-week CCRT regimen with MRI prior to and following external beam radiotherapy (EBRT) were retrospectively analyzed. Histogram features were calculated from volumes of interest (VOIs) contoured by a radiologist on ADC maps. Tumor volume, surface area, and descriptive statistics for the ADC voxel data, including mean, median, standard deviation, quantiles, skewness, and kurtosis were compared using a paired t-test.
Results: Post-EBRT scans were acquired an average of 41.4 days after baseline DWI. Tumor volume decreased by an average of 58.2±55.2 cm3 (p = 0.04) and surface area decreased by 9823±8011 mm2 (p = 0.03) from baseline. Mean ADC was 1184.8±169.5 10-6 mm2/s and 1342.0±172.2 10-6 mm2/s (p = 0.12) pre-CCRT and post-CCRT, respectively. Skewness and kurtosis were 0.82±0.16 and 4.56±1.36 pre-CCRT and 0.50±0.51 and 3.68±0.38 post-CCRT (p = 0.11 and p = 0.10).
Conclusion: Chemoradiotherapy resulted in increases in mean tumor ADC of locally advanced cervical carcinomas, with statistically significant decreases in tumor volume and surface area in this cohort. Future work will evaluate ADC of viable tumor subvolumes over time and correlate histogram features with treatment response.
Funding Support, Disclosures, and Conflict of Interest: This study was supported by the University of Texas MD Anderson Cancer Center Division of Radiation Oncology Radiation Oncology Strategic Initiatives (ROSI) Seed Grant Award Program.
Diffusion, MR, Target Localization