Adam Gladwish1, Ananth Ravi1, Lisa Barbera1, Lucas Mendez1, Melanie Davidson1, Laura D'Alimonte2, David D'Souza3, Matt Wronski1, Eric Leung4. 1. Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada. 2. Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. 3. Department of Oncology, London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada. 4. Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada. Electronic address: eric.leung@sunnybrook.ca.
Abstract
PURPOSE: To determine the dosimetric impact of organ and implant motion/deformation in the context of adaptive planning in image-guided gynecologic brachytherapy using a 3-fraction transperineal approach. METHODS AND MATERIALS: Twenty-six patients were analyzed. Each patient was treated with three fractions given over a 24-h period using a single insertion. A planning CT scan (±MRI) was acquired before the first fraction. A verification scan was taken within 1 h following the second fraction. A single plan was delivered for Fractions 1 and 2 with an adaptive plan delivered for Fraction 3. Two evaluation frameworks were established. Framework 1 investigated the effects of motion/deformation from both implant and organs. Framework 2 investigated the impact of implant motion/deformation alone. Differences in high-risk clinical target volume (HRCTV) D90%, V100%, and bladder/rectum D2cc were assessed. RESULTS: From implant to verification, the HRCTV D90% and V100% decreased significantly (5.0%, p < 0.01; 3.1%, p < 0.01) and rectal D2cc was significantly higher (12.2%, p = 0.02). Adaptive planning recouped these changes. Implant changes resulted in a reduction in HRCTV dose and coverage, but no significant effect was seen in the bladder or rectum. CONCLUSIONS: Adaptive planning represents an important aspect of perineal-based interstitial image-guided brachytherapy given in three fractions; its absence would result in plan degradation.
PURPOSE: To determine the dosimetric impact of organ and implant motion/deformation in the context of adaptive planning in image-guided gynecologic brachytherapy using a 3-fraction transperineal approach. METHODS AND MATERIALS: Twenty-six patients were analyzed. Each patient was treated with three fractions given over a 24-h period using a single insertion. A planning CT scan (±MRI) was acquired before the first fraction. A verification scan was taken within 1 h following the second fraction. A single plan was delivered for Fractions 1 and 2 with an adaptive plan delivered for Fraction 3. Two evaluation frameworks were established. Framework 1 investigated the effects of motion/deformation from both implant and organs. Framework 2 investigated the impact of implant motion/deformation alone. Differences in high-risk clinical target volume (HRCTV) D90%, V100%, and bladder/rectum D2cc were assessed. RESULTS: From implant to verification, the HRCTV D90% and V100% decreased significantly (5.0%, p < 0.01; 3.1%, p < 0.01) and rectal D2cc was significantly higher (12.2%, p = 0.02). Adaptive planning recouped these changes. Implant changes resulted in a reduction in HRCTV dose and coverage, but no significant effect was seen in the bladder or rectum. CONCLUSIONS: Adaptive planning represents an important aspect of perineal-based interstitial image-guided brachytherapy given in three fractions; its absence would result in plan degradation.
Authors: Andre Karius; Vratislav Strnad; Michael Lotter; Stephan Kreppner; Christoph Bert Journal: Strahlenther Onkol Date: 2022-03-12 Impact factor: 4.033