Dosimetric benefit of a library of plans versus single-plan strategy for pre-operative gastric cancer radiotherapy. (May 2023)

• Record Type: Journal Article
• Authors: Bleeker, Margot; Visser, Jorrit; Goudschaal, Karin; Bel, Arjan; Hulshof, Maarten C.C.M.; Sonke, Jan-Jakob; van der Horst, Astrid
• Is Part Of: Radiotherapy and oncology. Volume 182(2023)
• Publication Date: 2023-05
• Subjects: Adaptive radiotherapy -- Gastric cancer -- Library of plans -- Dose accumulation -- CBCT guidance; Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2023.109582
• Languages: English
• ISSNs: 0167-8140

Abstract

Highlights: A comprehensive roadmap for creating a model-based gastric LoP was presented. PTV margins for SP and LoP were calculated specifically for pre-op gastric cancer. SP and LoP were simulated and organ at risk (OAR) dose was accumulated. A LoP reduced the required PTV margin, average PTV and accumulated dose to OARs. A LoP potentially reduces risk for radiation-induced toxicities in gastric RT. Abstract: Background and purpose: The stomach experiences large volume and shape changes during pre-operative gastric radiotherapy. This study evaluates the dosimetric benefit for organs-at-risk (OARs) of a library of plans (LoP) compared to the traditional single-plan (SP) strategy. Materials and methods: Twelve patients who received SP CBCT-guided pre-operative gastric radiotherapy (45 Gy; 25 fractions) were included. Clinical target volume (CTV) consisted of CTVstomach (i.e., stomach + 10 mm uniform margin minus OARs) and CTVLN (i.e., regional lymph node stations). For LoP, five stomach volumes (approximately equidistant with fixed volumes) were created using a previously developed stomach deformation model (volume = 150–750 mL). Appropriate planning target volume (PTV) margins were calculated for CTVstomach (SP and LoP, separately) and CTVLN . Treatment plans were automatically generated/optimized and the best-fitting library plan was manually selected for each daily CBCT. OARs (i.e., liver, kidneys, heart, spleen, spinal canal) doses were accumulated and dose-volume histogram (DVH) parameters were evaluated. Results: The non-isotropic PTVstomach margins were significantly (p < 0.05) smaller for LoP than SP (median = 13.1 vs 19.8 mm). For each patient, the average PTV was smaller using a LoP (difference range 134–1151 mL). For all OARs except the kidneys, DVH parameters were significantly reduced using a LoP. Differences in mean dose (Dmean) for liver, heart and spleen ranged between −1.8 to 5.7 Gy. For LoP, a benefit of heart Dmean > 4 Gy and spleen Dmean > 2 Gy was found in 4 and 5 patients, respectively. Conclusion: A LoP strategy for pre-operative gastric cancer reduced average PTV and reduced OAR dose compared to a SP strategy, thereby potentially reducing risks for radiation-induced toxicities.