Effect of androgen deprivation and radiation therapy on MRI fiber tractography in prostate cancer: can we assess treatment response on imaging?

ABSTRACT

OBJECTIVE: To evaluate quantitative changes in Diffusion Tensor Magnetic Resonance Tractography in prostate cancer following androgen deprivation and radiation therapy. METHODS: 22 patients with elevated PSA and biopsy proven prostate carcinoma who underwent MRI of the prostate at 1.5 T with an endorectal coil were included. Group A) was the study group (n = 11), participants who underwent androgen deprivation and/or radiation therapy and group B) were Gleason-matched control group (n = 11) participants who did not undergo such therapy. Diffusion weighted images were used to generate three-dimensional (3D) map of fiber tracts from DTI. 3D regions of interest (ROI) were drawn over the tumor and healthy prostatic parenchyma in both groups to record tract number and tract density. Tumor region and normal parenchymal tract densities within each group were compared. RESULTS: Mean tract density in the tumor region and normal parenchyma was 2.3 and 3.3 in study group (tract numbers 116.6 and 170.2 respectively) and 1.6 and 2.7 in the control group respectively (tract numbers 252.5 and 346.3 respectively). The difference between these values was statistically significant for the control group (p = 0.0018) but not for the study group (p = 0.11). The difference between the tract numbers of tumor and normal parenchyma appears to narrow following therapy. CONCLUSION: The study demonstrated utility in using tractography as a biomarker in prostate cancer patients post treatment. ADVANCES IN KNOWLEDGE Quantitative DTI fiber tractography is a promising imaging biomarker to quantitatively assess treatment response in the setting of post-androgen deprivation and radiation therapy for prostate cancer.