The role of the urethrogram during simulation for localized prostate cancer

Area of Science:

• Radiation Oncology
• Medical Imaging

Background:

• Accurate definition of the treatment field's inferior border is critical for localized prostate cancer radiotherapy.
• Traditional methods using ischial tuberosities may lead to suboptimal margins.

Purpose of the Study:

• To evaluate the accuracy of urethrograms in defining the inferior border of the radiation treatment field for localized prostate cancer.
• To compare urethrogram-defined margins with those determined by ischial tuberosities.

Main Methods:

• Retrospective analysis of urethrograms from 89 patients with localized prostate cancer.
• Comparison of treatment field inferior borders defined by urethrograms versus ischial tuberosities.
• Assessment of margin adequacy and potential urethral dose.

Main Results:

• Urethrograms ensure a 2 cm margin, including 1 cm of proximal penile urethra.
• Using ischial tuberosities would result in inadequate margins for 25% of patients.
• Using ischial tuberosities could lead to excessive urethral irradiation in 11% of patients.
• Over one-third of patients would receive inappropriate inferior margins if relying solely on ischial tuberosities.
• No increased morbidity or toxicity was associated with urethrogram use.

Conclusions:

• Routine use of urethrograms during simulation is supported for localized prostate cancer.
• Defining the inferior border by ischial tuberosities carries an unacceptable risk of under- or overdosing.
• Urethrograms combined with CT provide accurate definition of the prostate apex and treatment margins.