Assessing Radiotherapy Responses in Low-Risk Prostate Cancer: A Longitudinal Analysis of T2 Relaxation Times

Rationale and Objectives To evaluate short and long-term changes in T 2 relaxation as a response to radiotherapy in patients with low and intermediate risk localized prostate cancer. Materials and Methods 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. Results Repeated Measures Analysis of Variance (RM-ANOVA) 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 ( M ) 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. Conclusion 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. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by Ministry of Health, Czech Republic - conceptual development of research organization (FNOs/2020) and by the Ministry of Education of Czech Republic under Project SP2023/042. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Informed consent form was obtained from all subjects and this study was approved by the Ethics Committee of University Hospital Ostrava, 17. listopadu 1790, 70852 Ostrava-Poruba, Czech Republic (Reference number: 967/2019). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors