Development of Prostate Bed Delineation Consensus Guidelines for Magnetic Resonance Image-Guided Radiotherapy and Assessment of Its Effect on Interobserver Variability

Post-Prostatectomy Magnetic Resonance-Guided Radiotherapy on a 1.5 Tesla Magnetic Resonance Integrated Linear Accelerator: Feasibility, Toxicity, and Preliminary Clinical Outcomes

INTRODUCTION

This study aimed to prospectively investigate magnetic resonance (MR)-guided radiotherapy (MRgRT) for post-prostatectomy prostate cancer and report preliminary clinical outcomes.

METHODS

All included patients underwent salvage or adjuvant adaptive MRgRT on a 1.5T MR integrated linear accelerator (MR-LINAC). Gastrointestinal and genitourinary toxicities were assessed. The primary endpoint was the progression-free survival (PFS) rate estimated by Kaplan-Meier (KM) survival analysis. A progression event was defined as the first occurrence of biochemical failure, radiological progression, or death. Secondary endpoints were biochemical failure-free survival (bFFS) rate, radiological PFS (rPFS) rate, and ≥G2 adverse events.

RESULTS

Thirty post-prostatectomy patients were enrolled and followed (median follow-up: 32.0 months; 3.0-48.1 months). Three patients had biochemical failure during follow-up. One patient developed pelvic node metastases. All patients were alive. The estimated PFS rates were 96.4% (95% confidence interval [95%CI]: 89.8%-100.0%) at 2 years and 78.8% (95%CI: 61.3%-100%) at 3 years. The estimated bFFS rates were 96.4% (95%CI: 89.8%-100%) /86.6%(95%CI: 73.4%-100%) at 2/3 years, respectively. The corresponding rPFS rates were 100% at 2 years and 92.3% (95%CI: 78.9%-100%) at 3 years, respectively. There was only one acute G2 GI adverse event (1/30, 3.33%) of abdominal pain occurred. Two late G2 events (one rectal bleeding and one urinary frequency) were scored (2/30, 6.67%). No ≥G3 events were observed.

CONCLUSION

Our findings suggest the feasibility, excellent patient tolerance, and encouraging efficacy of post-prostatectomy MRgRT, extending our knowledge of the clinical outcomes of MRgRT and serving as a benchmark for future investigation.

Delineation of target volume by radiation therapists during online adaptive radiation therapy: What authorization?

The evolution of radiation therapy techniques goes hand in hand with the evolution of the profession of radiation therapist. In the particular context of online adaptive radiotherapy based on cone beam computed tomography images, delegation of certain tasks from the physician to the radiation therapist is possible within the framework of a cooperation protocol. This delegation requires prior theoretical and practical training. It enriches the practice of radiation therapists by allowing them to acquire new skills and greater autonomy. It foreshadows access for radiation therapists to advanced practice.

Urethra contouring on computed tomography urethrogram versus magnetic resonance imaging for stereotactic body radiotherapy in prostate cancer

Accurate urethra contouring is critical in prostate SBRT. We compared urethra contouring on CT-urethrogram and T2-weighted MRI. The dice similarity coefficient, Jaccard index, Hausdorff distance and mean distance to agreement were evaluated. All four metrics indicate better agreement and less variability in urethra contouring on CT-urethrogram, compared to T2-weighted MRI.