Anatomic-based three-dimensional planning precludes use of catheter-delivered contrast for treatment of prostate cancer.

PURPOSE: Retrograde urethrography is a standard method to identify the prostatic apex during planning for prostate cancer radiotherapy. This is an invasive and uncomfortable procedure. With modern three-dimensional computed tomography planning, we explored whether retrograde urethrography was still necessary to accurately identify the prostatic apex. METHODS AND MATERIALS: Fifteen patients underwent computed tomography simulation with and without bladder, urethral, and rectal contrast. The prostatic base and apex were identified on both scans, using contrast and anatomy, respectively. The anatomic location of the prostatic apex as defined by these methods was confirmed in another 57 patients with postbrachytherapy imaging. RESULTS: The prostatic base and apex were within a mean of 3.8 mm between the two scans. In every case, the beak of the retrograde urethrogram abutted the line drawn parallel to, and bisecting, the pubic bone on the lateral films. With these anatomic relationships defined, in the postbrachytherapy patients, the distance from the prostatic apex to the point at which the urethra traversed the pelvic floor was an average of 11.7 mm. On lateral films, we found that the urethra exited the pelvis an average of 16.6 mm below the posterior-most fusion of the pubic symphysis. On axial images, this occurred at a mean separation of the ischia of about 25 mm. CONCLUSION: With a knowledge of the anatomic relationships and modern three-dimensional computed tomography planning equipment, the prostatic apex can be easily and consistently identified, obviating the need to subject patients to retrograde urethrography.

Dosimetric Evaluation of Pinnacle's Automated Treatment Planning Software to Manually Planned Treatments.

INTRODUCTION: With the advent of complex treatment techniques like volumetric modulated arc therapy, there has been increasing interest in treatment planning technologies aimed at reducing planning time. One of these such technologies is auto-planning, which is an automated planning module within Pinnacle3. This study seeks to retrospectively evaluate the dosimetric quality of auto-planning-derived treatment plans as they compare to manual plans for intact prostate, prostate and lymph nodes, and brain treatment sites. MATERIALS AND METHODS: Previous clinical plans were used to generate site-specific auto-planning templates. These templates were used to compare the 3 evaluated treatment sites. Plans were replanned using auto-planning and compared to the clinically delivered plans. For the planning target volume, the following metrics were evaluated: homogeneity index, conformity index, D2cc, Dmean, D2%, D98%, and multiple dose fall-off parameters. For the organs at risk, D2cc, Dmean, and organ-specific clinical metrics were evaluated. Statistical differences were evaluated using a Wilcoxon paired signed-rank test with a significance level of 0.05. Statistically significant ( P < 0.05) differences were noted in organs at risk sparing. RESULTS: For the prostate, there was as much as 6.8% reduction in bladder Dmean and 23.5% reduction in penile bulb Dmean. For the prostate + lymph nodes, decreases in Dmean values ranging from 4.1% in the small bowel to 22.3% in the right femoral head were observed. For brain, significant improvements were observed in Dmax and Dmean to most organs at risk. CONCLUSION: Our study showed improved organs at risk sparing in most organs while maintaining planning target volume coverage. Overall, auto-planning can generate plans that delivered the same target coverage as the clinical plans but offered significant reductions in mean dose to organs at risk.

Comparison of composite prostate radiotherapy plan doses with dependent and independent boost phases.

Prostate cases commonly consist of dual phase planning with a primary plan followed by a boost. Traditionally, the boost phase is planned independently from the primary plan with the risk of generating hot or cold spots in the composite plan. Alternatively, boost phase can be planned taking into account the primary dose. The aim of this study was to compare the composite plans from independently and dependently planned boosts using dosimetric and radiobiological metrics. Ten consecutive prostate patients previously treated at our institution were used to conduct this study on the Raystation™ 4.0 treatment planning system. For each patient, two composite plans were developed: a primary plan with an independently planned boost and a primary plan with a dependently planned boost phase. The primary plan was prescribed to 54 Gy in 30 fractions to the primary planning target volume (PTV1) which includes prostate and seminal vesicles, while the boost phases were prescribed to 24 Gy in 12 fractions to the boost planning target volume (PTV2) that targets only the prostate. PTV coverage, max dose, median dose, target conformity, dose homogeneity, dose to OARs, and probabilities of benefit, injury, and complication-free tumor control (P+) were compared. Statistical significance was tested using either a 2-tailed Student's t-test or Wilcoxon signed-rank test. Dosimetrically, the composite plan with dependent boost phase exhibited smaller hotspots, lower maximum dose to the target without any significant change to normal tissue dose. Radiobiologically, for all but one patient, the percent difference in the P+ values between the two methods was not significant. A large percent difference in P+ value could be attributed to an inferior primary plan. The benefits of considering the dose in primary plan while planning the boost is not significant unless a poor primary plan was achieved.