Poster - Thur Eve - 28: Optimization of a prostate cancer IGRT protocol

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Image-guided radiation therapy (IGRT) using kV cone beam computed tomography (CBCT) is resource-intensive and delivers dose to normal tissues.
• Current IGRT protocols for post-prostatectomy patients rely on daily couch shifts to align surgical clips, posing challenges for accuracy due to anatomical variations.

Purpose of the Study:

• To evaluate the clinical effectiveness and resource implications of the standard daily IGRT protocol against two alternatives: no IGRT and an alternating day IGRT strategy.
• To assess dose-volume statistics for target volumes and organs at risk under different IGRT scenarios.

Main Methods:

• A novel method was employed to deform planning CT datasets to daily CBCT acquisitions, calculate dose on deformed datasets, and transform dose back to the planning CT.
• Dose-volume histograms (DVHs) were analyzed for six post-prostatectomy patients under three IGRT conditions: no IGRT, daily IGRT, and alternating day IGRT.

Main Results:

• Clinical target volume doses deviated by 3.2%, 1.3%, and 2.1% for non-IGRT, daily IGRT, and alternating day IGRT, respectively.
• Organs at risk doses deviated by up to 10.5%, 13.1%, and 10.7% for non-IGRT, daily IGRT, and alternating day IGRT, respectively.
• Significant deviations between IGRT and non-IGRT were not always observed, indicating limitations in correcting prostate bed deformations with couch shifts.

Conclusions:

• Alternating day IGRT offers a clinically acceptable alternative to daily IGRT, significantly reducing resource utilization and patient imaging dose.
• The findings suggest that optimizing IGRT frequency can balance treatment accuracy with efficiency and reduced radiation exposure in post-prostatectomy patients.