| Title: |
Interfractional Geometric Variations and Dosimetric Benefits of Stereotactic MRI Guided Online Adaptive Radiotherapy (SMART) of Prostate Bed after Radical Prostatectomy: Post-Hoc Analysis of a Phase II Trial |
| Authors: |
Cao, Minsong; Gao, Yu; Yoon, Stephanie M; Yang, Yingli; Sheng, Ke; Ballas, Leslie K; Basehart, Vincent; Sachdeva, Ankush; Felix, Carol; Low, Daniel A; Steinberg, Michael L; Kishan, Amar U |
| Source: |
Cancers, vol 13, iss 11 |
| Publisher Information: |
eScholarship, University of California |
| Publication Year: |
2021 |
| Collection: |
University of California: eScholarship |
| Subject Terms: |
32 Biomedical and Clinical Sciences (for-2020); 3202 Clinical Sciences (for-2020); 3211 Oncology and Carcinogenesis (for-2020); Clinical Research (rcdc); Biomedical Imaging (rcdc); Urologic Diseases (rcdc); Cancer (rcdc); Clinical Trials and Supportive Activities (rcdc); Radiation Oncology (rcdc); 6.5 Radiotherapy and other non-invasive therapies (hrcs-rac); Cancer (hrcs-hc); stereotactic body radiotherapy SBRT; post-prostatectomy; prostate cancer; MR guided adaptive radiotherapy; MRgRT; 1112 Oncology and Carcinogenesis (for) |
| Time: |
2802 |
| Description: |
PURPOSE: To evaluate geometric variations of patients receiving stereotactic body radiotherapy (SBRT) after radical prostatectomy and the dosimetric benefits of stereotactic MRI guided adaptive radiotherapy (SMART) to compensate for these variations. MATERIALS/METHODS: The CTV and OAR were contoured on 55 MRI setup scans of 11 patients treated with an MR-LINAC and enrolled in a phase II trial of post-prostatectomy SBRT. All patients followed institutional bladder and rectum preparation protocols and received five fractions of 6-6.8 Gy to the prostate bed. Interfractional changes in volume were calculated and shape deformation was quantified by the Dice similar coefficient (DSC). Changes in CTV-V95%, bladder and rectum maximum dose, V32.5Gy and V27.5Gy were predicted by recalculating the initial plan on daily MRI. SMART was retrospectively simulated if the predicted dose exceeded pre-set criteria. RESULTS: The CTV volume and shape remained stable with a median volumetric change of 3.0% (IQR -3.0% to 11.5%) and DSC of 0.83 (IQR 0.79 to 0.88). Relatively large volumetric changes in bladder (median -24.5%, IQR -34.6% to 14.5%) and rectum (median 5.4%, IQR - 9.7% to 20.7%) were observed while shape changes were moderate (median DSC of 0.79 and 0.73, respectively). The median CTV-V95% was 98.4% (IQR 94.9% to 99.6%) for the predicted doses. However, SMART would have been deemed beneficial for 78.2% of the 55 fractions based on target undercoverage (16.4%), exceeding OAR constraints (50.9%), or both (10.9%). Simulated SMART improved the dosimetry and met dosimetric criteria in all fractions. Moderate correlations were observed between the CTV-V95% and target DSC (R2 = 0.73) and bladder mean dose versus volumetric changes (R2 = 0.61). CONCLUSIONS: Interfractional dosimetric variations resulting from anatomic deformation are commonly encountered with post-prostatectomy RT and can be mitigated with SMART. |
| Document Type: |
article in journal/newspaper |
| File Description: |
application/pdf |
| Language: |
unknown |
| Relation: |
qt1n56q8zx; https://escholarship.org/uc/item/1n56q8zx; https://escholarship.org/content/qt1n56q8zx/qt1n56q8zx.pdf |
| DOI: |
10.3390/cancers13112802 |
| Availability: |
https://escholarship.org/uc/item/1n56q8zx; https://escholarship.org/content/qt1n56q8zx/qt1n56q8zx.pdf; https://doi.org/10.3390/cancers13112802 |
| Rights: |
CC-BY |
| Accession Number: |
edsbas.B83BC223 |
| Database: |
BASE |