Conformal prostate brachytherapy guided by realtime dynamic dose calculations using permanent 125iodine implants:...

Area of Science:

• Urology
• Radiation Oncology
• Medical Physics

Background:

• Low-dose-rate (LDR) prostate brachytherapy uses 125I or 103Pd seeds for low-risk prostate cancer.
• Anatomical changes during brachytherapy can lead to inaccurate dose delivery compared to pre-planning.
• Post-implant CT dosimetry is standard but time-consuming and costly.

Purpose of the Study:

• To report on a novel technique for interactive, real-time, intra-operative dose calculation in LDR prostate brachytherapy.
• To evaluate the feasibility and preliminary outcomes of this dynamic planning approach.
• To compare toxicity rates with traditional post-implant dosimetry methods.

Main Methods:

• Implementation of interactive real-time dynamic intra-operative dose calculation.
• Real-time seed placement adjustments based on intra-operative dosimetry.
• Avoidance of post-implant CT for final dosimetry.
• Analysis of dosimetric parameters (V90, V150, V200, D90) and toxicity outcomes.

Main Results:

• Median V90 of 98%, V150 of 60%, and V200 of 24%.
• Median intra-operative D90 was 16,817 cGy.
• Reduced acute genitourinary (GU) toxicity (grade 1&2) from 28% to 16% and chronic GU toxicity from 16% to 11%.
• Acute urinary retention occurred in 3% of patients.

Conclusions:

• Real-time intra-operative planning in LDR prostate brachytherapy is successfully implemented.
• This method enhances seed placement accuracy, leading to improved dose delivery.
• The technique significantly reduces acute and chronic GU morbidity and eliminates the need for post-implant CT dosimetry.