Longitudinal analysis of T2 relaxation time variations following radiotherapy for prostate cancer

Aim of this paper is to evaluate short and long-term changes in T2 relaxation times after radiotherapy in patients with low and intermediate risk localized prostate cancer. A total of 24 patients were selected for this retrospective study. Each participant underwent 1.5T magnetic resonance imaging on seven separate occasions: initially after the implantation of gold fiducials, the required step for Cyberknife therapy guidance, followed by MRI scans two weeks post -therapy and monthly thereafter. As part of each MRI scan, the prostate region was manually delineated, and the T-2 relaxation times were calculated for quantitative analysis. The T-2 relaxation times between individual follow-ups were analyzed using Repeated Measures Analysis of Variance that revealed a significant difference across all measurements (F (6, 120) = 0.611, p << 0.001). A Bonferroni post hoc test revealed significant differences in median T-2 values between the baseline and subsequent measurements, particularly between pre -therapy (M0) and two weeks post -therapy (M-1), as well as during the monthly interval checks (M-2 - M-6). Some cases showed a delayed decrease in relaxation times, indicating the prolonged effects of therapy. The changes in T-2 values during the course of radiotherapy can help in monitoring radiotherapy response in unconfirmed patients, quantifying the scarring process, and recognizing the therapy failure.