Purpose: Outcome evaluation in ocular adnexal lymphoma (OAL) is based on clinical assessment and conventional volumetric changes in tumor size. The purpose of this retrospective study was to compare if changes in apparent diffusion coefficient (ADC) tumor values obtained by diffusion-weighted MRI corresponded to changes in enhancing tumor volume in the evaluation of early treatment response or failure in patients with OAL.
Methods: A retrospective case series analysis of conventional contrast-enhanced orbital MRI and diffusion-weighted sequences was performed on 8 pathologically confirmed OAL tumors before and after therapy. Mean ADC values and normalized ADC ratios were obtained using a region-of-interest analysis method on enhancing OAL lesions; tumor volumes were calculated using a manual segmentation method. Changes in tumor volume, mean ADC tumor values, and normalized ADC ratios were compared before and after therapy using a Wilcoxon rank-sum test.
Results: Overall, a significant difference was found in mean ADC values and normalized ADC ratios within OAL tumors before and after therapy (p < 0.05), irrespective of the type of therapy administered. There was a trend toward decreased mean enhancing tumor volume after therapy (p = 0.161). An increase in ADC values and a decrease in enhancing tumor volume after therapy correlated with a positive treatment response in 7 of 8 tumors; a decrease in ADC values and an increase in enhancing tumor volume after therapy correlated with a negative treatment response in 1 of 8 tumors.
Conclusions: Tracking changes in tumor ADC values after various treatment regimens for OAL may be useful in predicting early treatment response or failure and can provide complementary information that corresponds to conventional volume changes in tumor size. Further validation of these preliminary results in larger prospective randomized trials is needed.