Cesar Della Biancia1, Ellen Yorke1, Marisa A Kollmeier2. 1. Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York. 2. Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York. Electronic address: kollmeim@mskcc.org.
Abstract
PURPOSE: To determine bladder wall position variability during external beam radiation therapy (EBRT) for bladder cancer with intravesical fiducial markers using 2-dimensional (2D) and volumetric (3D) imaging registration. METHODS AND MATERIALS: Twenty T2-4aN0-1 bladder cancer patients underwent definitive EBRT with concurrent chemotherapy between May 2001 and January 2012, and had intravesical fiducial marker placement before simulation. Computed tomographic (CT)-based treatment planning was used for an initial phase to deliver 45 Gy (1.8 Gy/fraction) to the bladder and pelvic lymphatics followed by a boost to the involved bladder wall for an additional 21.6 Gy (1.8 Gy/fraction). Orthogonal kilovoltage radiograph images (34-37 images/patient) were obtained daily, registered with digitally reconstructed radiographs from the planning scan. Translational corrections were made daily. A kilovoltage cone-beam CT (kVCBCT) was acquired weekly and its registration with the planning scan was compared with that day's 2D registration results. RESULTS: Of 739 treatments, 6% resulted in ≥15 mm displacement in 1 or more directions and 26% resulted in ≥10 mm displacement in 1 or more directions. Based on 2D registrations, the average millimeter difference between bony registration and fiducial marker registration (BR-FMR) in the right-left (RL) (R+), anterior-posterior (AP) (A+), and superior-inferior (SI) (I+) directions were: 0.5 ± 1.0 (range, -2.0 to +3.8), 1.7 ± 4.4 (range, -8.1 to +13.5) and -3.7 ± 5.8 (range, -16.8 to +8.3), respectively. For kVCBCT registrations, the average mm difference in the RL, AP, and SI directions were 0.3 ± 2.1 (range, -2.4 to +5.1), 3.1 ± 5.9 (range, -2.9 to +13.3) and -4.8 ± 8.0 (range, -16.4 to +9.5), respectively. CONCLUSIONS: Using intravesical fiducial markers, the largest difference in bladder motion based BR-FMR differences was in the superior-inferior direction. Because fiducial markers are target surrogates, setup using bony anatomy alone can lead to target displacements up to 13.5 mm anteriorly and 16.8 mm superiorly. This confirms a 1.5-1.7 cm minimum in planning target margins. These findings suggest a significant advantage in using intravesical fiducial markers to determine daily translational corrections.
PURPOSE: To determine bladder wall position variability during external beam radiation therapy (EBRT) for bladder cancer with intravesical fiducial markers using 2-dimensional (2D) and volumetric (3D) imaging registration. METHODS AND MATERIALS: Twenty T2-4aN0-1 bladder cancerpatients underwent definitive EBRT with concurrent chemotherapy between May 2001 and January 2012, and had intravesical fiducial marker placement before simulation. Computed tomographic (CT)-based treatment planning was used for an initial phase to deliver 45 Gy (1.8 Gy/fraction) to the bladder and pelvic lymphatics followed by a boost to the involved bladder wall for an additional 21.6 Gy (1.8 Gy/fraction). Orthogonal kilovoltage radiograph images (34-37 images/patient) were obtained daily, registered with digitally reconstructed radiographs from the planning scan. Translational corrections were made daily. A kilovoltage cone-beam CT (kVCBCT) was acquired weekly and its registration with the planning scan was compared with that day's 2D registration results. RESULTS: Of 739 treatments, 6% resulted in ≥15 mm displacement in 1 or more directions and 26% resulted in ≥10 mm displacement in 1 or more directions. Based on 2D registrations, the average millimeter difference between bony registration and fiducial marker registration (BR-FMR) in the right-left (RL) (R+), anterior-posterior (AP) (A+), and superior-inferior (SI) (I+) directions were: 0.5 ± 1.0 (range, -2.0 to +3.8), 1.7 ± 4.4 (range, -8.1 to +13.5) and -3.7 ± 5.8 (range, -16.8 to +8.3), respectively. For kVCBCT registrations, the average mm difference in the RL, AP, and SI directions were 0.3 ± 2.1 (range, -2.4 to +5.1), 3.1 ± 5.9 (range, -2.9 to +13.3) and -4.8 ± 8.0 (range, -16.4 to +9.5), respectively. CONCLUSIONS: Using intravesical fiducial markers, the largest difference in bladder motion based BR-FMR differences was in the superior-inferior direction. Because fiducial markers are target surrogates, setup using bony anatomy alone can lead to target displacements up to 13.5 mm anteriorly and 16.8 mm superiorly. This confirms a 1.5-1.7 cm minimum in planning target margins. These findings suggest a significant advantage in using intravesical fiducial markers to determine daily translational corrections.
Authors: Matthew D Greer; Stephanie K Schaub; Stephen R Bowen; Jay J Liao; Kenneth Russell; Jonathan J Chen; Emily S Weg; Juergen Meyer; Tristan Alving; George R Schade; John L Gore; Sarah P Psutka; Robert B Montgomery; Michael Schweizer; Evan Y Yu; Petros Grivas; Jonathan L Wright; Jing Zeng Journal: Adv Radiat Oncol Date: 2021-11-21
Authors: Kathleene Dower; Andriana Ford; Michael Sandford; Andrew Doherty; Stuart Greenham; Luke Kerin; Patrick Dwyer; Carmen Hansen; Justin Westhuyzen; Thomas Shakespeare Journal: J Med Radiat Sci Date: 2021-07-20