학술논문
Impact on dose distribution and volume changes of a bioabsorbable polyglycolic acid spacer during chemo-proton therapy for a pediatric Ewing sarcoma
Document Type
Academic Journal
Author
Source
Journal of Radiation Research. November 2020, Vol. 61 Issue 6, p952, 7 p.
Subject
Language
English
ISSN
0449-3060
Abstract
INTRODUCTION Recent advances in multidisciplinary treatment have improved the survival of pediatric cancer patients, but in exchange, they face the problem of living with late complications [1-4]. Although radiotherapy plays [...]
The clinical utility of a recently developed bioabsorbable polyglycolic acid (PGA) spacer has not yet been established in pediatric patients; therefore, we aimed to investigate its utility during chemo-proton therapy for pediatric cancer. Proton depth-dose curves were obtained in a water phantom with or without the spacer. Computed tomography (CT) scans were performed for the PGA spacer immersed in saline for 2 weeks to measure CT numbers and estimate the relative stopping power (RSP) for the proton beams. The spacer was placed in a patient with sacral Ewing sarcoma receiving 55.8 Gy [relative biological effectiveness (RBE)] in 31 fractions and was evaluated using CT scans performed every other week. In addition, the images were used to quantitatively evaluate changes in volume and RSP of the spacer and dosedistributionsinnormaltissues. The spacerimmersedinsaline hadaCTnumberof91[+ or -]7(mean[+ or -]standard deviation) Hounsfield units, and the corresponding RSP was predicted to be 1.07 [+ or -] 0.01. The measured RSP agreed with the predicted one. The volumes of the large bowel and rectum receiving [greater than or equal to]45 Gy(RBE) ([V.sub.45Gy]) were significantly reduced by placing the spacer; [V.sub.45Gy] without and with the spacer were 48.5 and 0.01%, respectively, for the rectum and 7.2 and 0%, respectively, for the large bowel. The volume of the spacer and RSP decreased at rates of 4.6 and 0.44% per week, respectively, whereas the target dose coverage was maintained until the end of treatment. The PGA spacer was considered effective for pediatric cancer patients undergoing chemo-proton therapy. Keywords: polyglycolic acid (PGA) spacer; pediatric cancer; chemo-proton therapy; volume changes
The clinical utility of a recently developed bioabsorbable polyglycolic acid (PGA) spacer has not yet been established in pediatric patients; therefore, we aimed to investigate its utility during chemo-proton therapy for pediatric cancer. Proton depth-dose curves were obtained in a water phantom with or without the spacer. Computed tomography (CT) scans were performed for the PGA spacer immersed in saline for 2 weeks to measure CT numbers and estimate the relative stopping power (RSP) for the proton beams. The spacer was placed in a patient with sacral Ewing sarcoma receiving 55.8 Gy [relative biological effectiveness (RBE)] in 31 fractions and was evaluated using CT scans performed every other week. In addition, the images were used to quantitatively evaluate changes in volume and RSP of the spacer and dosedistributionsinnormaltissues. The spacerimmersedinsaline hadaCTnumberof91[+ or -]7(mean[+ or -]standard deviation) Hounsfield units, and the corresponding RSP was predicted to be 1.07 [+ or -] 0.01. The measured RSP agreed with the predicted one. The volumes of the large bowel and rectum receiving [greater than or equal to]45 Gy(RBE) ([V.sub.45Gy]) were significantly reduced by placing the spacer; [V.sub.45Gy] without and with the spacer were 48.5 and 0.01%, respectively, for the rectum and 7.2 and 0%, respectively, for the large bowel. The volume of the spacer and RSP decreased at rates of 4.6 and 0.44% per week, respectively, whereas the target dose coverage was maintained until the end of treatment. The PGA spacer was considered effective for pediatric cancer patients undergoing chemo-proton therapy. Keywords: polyglycolic acid (PGA) spacer; pediatric cancer; chemo-proton therapy; volume changes