Empty Versus Full Bladder Protocols in Radiotherapy Planning for Localised Prostate Cancer: A Dosimetric Study

Area of Science:

• Radiation Oncology
• Medical Physics
• Urology

Background:

• Full bladder preparation is standard for prostate radiotherapy, aiming to shield organs at risk.
• However, achieving consistent full bladder volumes is challenging and can extend treatment planning times.

Purpose of the Study:

• To evaluate the dosimetric and volumetric differences between full and empty bladder preparations for prostate radiotherapy planning.
• To assess the impact of bladder volume on target coverage and organ-at-risk sparing.

Main Methods:

• CT simulations were performed on 20 prostate cancer patients with both full and empty bladders.
• Volumetric Modulated Arc Therapy (VMAT) plans were generated for both conditions, prescribing 60Gy/20 fractions with a simultaneous integrated boost to 66Gy for dominant intraprostatic lesions.
• Key dosimetric endpoints, including bladder and rectal V30 and V60, and planning target volume (PTV) coverage, were compared using paired t-tests.

Main Results:

• Empty bladder volumes were significantly smaller than full bladder volumes (median 126.4 cm³ vs. 276.0 cm³).
• Clinical target volume (CTV) volumes and PTV coverage remained comparable between the two preparations.
• Rectal V30 was significantly reduced with empty bladder planning (15.6% vs. 19.9%), while bladder V30 increased (26.9% vs. 20.7%).

Conclusions:

• Empty bladder planning for prostate radiotherapy is a viable alternative that maintains target coverage and PTV dose.
• This method significantly reduces rectal dose and may improve patient comfort and workflow efficiency.
• The observed increase in bladder V30 is acceptable as other bladder dose constraints were met.