Estimating PTV Margins in Head and Neck Stereotactic Ablative Radiation Therapy (SABR) Through Target Site Analysis of Positioning and Intrafractional Accuracy

Autor: Shane Mesko, S. Tung, Bhavana V. Chapman, Jack Phan, He Wang, Jay Reddy, Congjun Wang, G. Brandon Gunn, Steven J. Frank, Adam S. Garden, Dario Pasalic, William H. Morrison, Amy C. Moreno, David I. Rosenthal, Clifton D. Fuller
Rok vydání: 2020
Předmět:
Cancer Research
Cone beam computed tomography
medicine.medical_treatment
Radiotherapy Setup Errors
Radiosurgery
SABR volatility model
Skull Base Neoplasms
Patient Positioning
Article
Re-Irradiation
030218 nuclear medicine & medical imaging
Immobilization
03 medical and health sciences
0302 clinical medicine
Ablative case
Humans
Medicine
Radiology
Nuclear Medicine and imaging
Prospective Studies
Aged
Radiation
business.industry
Radiotherapy Planning
Computer-Assisted
Dose fractionation
Cone-Beam Computed Tomography
Middle Aged
Quality Improvement
Parotid Neoplasms
Radiation therapy
Skull
medicine.anatomical_structure
Oncology
Target site
Head and Neck Neoplasms
030220 oncology & carcinogenesis
Dose Fractionation
Radiation
Neoplasm Recurrence
Local
business
Nuclear medicine
Radiotherapy
Image-Guided
Zdroj: Int J Radiat Oncol Biol Phys
ISSN: 0360-3016
Popis: Recurrent or previously irradiated head and neck cancers (HNC) are therapeutically challenging and may benefit from high-dose, highly accurate radiation techniques, such as stereotactic ablative radiation therapy (SABR). Here, we compare set-up and positioning accuracy across HNC subsites to further optimize the treatment process and planning target volume (PTV) margin recommendations for head and neck SABR.We prospectively collected data on 405 treatment fractions across 79 patients treated with SABR for recurrent/previously irradiated HNC. First, interfractional error was determined by comparing ExacTrac x-ray to the treatment plan. Patients were then shifted and residual error was measured with repeat x-ray. Next, cone beam computed tomography (CBCT) was compared with ExacTrac for positioning agreement, and final shifts were applied. Lastly, intrafractional error was measured with x-ray before each arc. Results were stratified by treatment site into skull base, neck/parotid, and mucosal.Most patients (66.7%) were treated to 45 Gy in 5 fractions (range, 21-47.5 Gy in 3-5 fractions). The initial mean ± standard deviation interfractional errors were -0.2 ± 1.4 mm (anteroposterior), 0.2 ± 1.8 mm (craniocaudal), and -0.1 ± 1.7 mm (left-right). Interfractional 3-dimensional vector error was 2.48 ± 1.44, with skull base significantly lower than other sites (2.22 vs 2.77; P = .0016). All interfractional errors were corrected to within 1.3 mm and 1.8°. CBCT agreed with ExacTrac to within 3.6 mm and 3.4°. CBCT disagreements and intrafractional errors of1 mm or1° occurred at significantly lower rates in skull base sites (CBCT: 16.4% vs 50.0% neck, 52.0% mucosal, P.0001; intrafractional: 22.0% vs 48.7% all others, P.0001). Final PTVs were 1.5 mm (skull base), 2.0 mm (neck/parotid), and 1.8 mm (mucosal).Head and neck SABR PTV margins should be optimized by target site. PTV margins of 1.5 to 2 mm may be sufficient in the skull base, whereas 2 to 2.5 mm may be necessary for neck and mucosal targets. When using ExacTrac, skull base sites show significantly fewer uncertainties throughout the treatment process, but neck/mucosal targets may require the addition of CBCT to account for positioning errors and internal organ motion.
Databáze: OpenAIRE
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