2007 - Dosimetric Comparison of Scheduled and Adaptive Planning for Bladder Cancer Treatment Using CT-Based Online Adaptive System
Presenter(s)
A. Amoush1, V. Arora1, R. Rajkumar1, K. M. Daniell1, M. Patel2, C. S. Spina2, I. Deutsch1, and A. C. Riegel1; 1Department of Radiation Oncology, Columbia University Irving Medical Center, New York, NY, 2Columbia University Irving Medical Center, New York, NY
Purpose/Objective(s): To evaluate the cumulative dosimetric differences between scheduled and adaptive treatment plans for bladder cancer patients treated with online adaptive system, incorporating clinically relevant dose constraints to assess target coverage and organ-at-risk (OAR) sparing
Materials/Methods: Three bladder cancer patients underwent CT-based online adaptive planning, receiving a prescribed dose of 55 Gy in 20 fractions. This study analyzed 60 fractions, deforming the dose from each fraction to the planning CT and summing the deformed doses for both the scheduled and adaptive plans.
Dosimetric parameters analyzed included target coverage, with PTV_55 constraints defined by a minimum dose of =90%, a maximum dose of =110%, and V95% coverage of =98%. Coverage metrics for CTV_55 included V98% and V95%. For bowel dose constraints, the evaluated volumes were V37.5Gy (<116cc), V41.7Gy (<104cc), V45.8Gy (<91cc), V50Gy (<73cc), V54.2Gy (<23cc), and V58.3Gy (<0cc). Similarly, for the rectum, dose-volume constraints included V25Gy (<80%), V41.7Gy (<60%), V50Gy (<50%), V54.2Gy (<30%), and V58.3Gy (<15%).Results: The deformed 3D summed dose distribution and dose-volume histograms (DVH) were compared between scheduled and adaptive plans. The adaptive plan improved target dose coverage while maintaining OAR doses within constraints. The results are provided in the table at the end, following the conclusion section.
Conclusion: The online adaptive planning system successfully improved target dose coverage while maintaining OAR doses within tolerance limits. Although some OARs received higher doses with adaptive planning compared to the scheduled approach, all remained within acceptable thresholds. This increase may be attributed to OAR displacement. The adaptive approach effectively accounted for daily variations in bladder filling and organ displacement, leading to better dose delivery to the target without exceeding constraints.
Abstract 2007 - Table 1 The p-values indicate no statistically significant differences in most dose metrics, though the adaptive plan showed improved target coverage while maintaining bowel and rectum doses within clinical tolerances.| Metric | Scheduled Plan | Adaptive Plan | p-value |
| PTV_55 Min Dose (%) | 76.1% ± 10.1% | 89.5% ± 4.6% | 0.3 |
| PTV_55 Max Dose (%) | 108.2% ± 2.5% | 106.6% ± 0.41% | 0.4 |
| PTV_55 V95% Coverage (%) | 92.6% ± 5.1% | 98.6% ± 0.34% | 0.3 |
| CTV_55 V98% Coverage (%) | 97.8% ± 1.73% | 99.9% ± 0.17% | 0.3 |
| CTV_55 V95% Coverage (%) | 99.3% ± 0.75% | 100% ± 0.01% | 0.3 |
| Bowel V37.5Gy (cc) | 77.6 ± 11.3 | 105.1 ± 18 | 0.3 |
| Bowel V41.7Gy (cc) | 54.5 ± 13.2 | 81.1 ± 12.3 | 0.3 |
| Bowel V45.8Gy (cc) | 35.6 ± 12.8 | 62.4 ± 9.2 | 0.2 |
| Bowel V50Gy (cc) | 18.1 ± 9.8 | 44.6 ± 8.2 | 0.2 |
| Bowel V54.2Gy (cc) | 23.5 ± 7.4 | 23.5 ± 7.4 | 0.2 |
| Bowel V58.3Gy (cc) | 0 | 0 | - |
| Rectum V25Gy (%) | 47.2% ± 15.1% | 52.6% ± 15% | 0.2 |
| Rectum V41.7Gy (%) | 9.6% ± 5.3% | 7.9% ± 3.1% | 0.6 |
| Rectum V50Gy (%) | 3.6% ± 1.7% | 2.4% ± 1.4% | 0.6 |
| Rectum V54.2Gy (%) | 1.2% ± 0.1% | 1.1% ± 0.8% | 0.9 |