Ang Gao1, Shijiang Wang1, Zheng Fu2, Xindong Sun1, Jinming Yu1, Xue Meng1. 1. Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong Academy of Medical Sciences Jinan, China. 2. Department of Nuclear Medicine, Shandong Cancer Hospital and Institute Jinan, China.
Abstract
BACKGROUND: To investigate whether during/post-radiotherapy FDG uptake locations within tumors is likely identified using a pre-radiotherapy scan for non-small cell lung cancer (NSCLC), ultimately enabling confirm that a suitable metabolically active sub-volume pre-radiotherapy of the primary tumor for radiation boosting target. METHODS: Patients with a pathologically proven inoperable stage II-III NSCLC were enrolled. For each patient, one pre-radiotherapy (pre-RT) plus one following 40Gy during-radiotherapy (during-RT) or post-radiotherapy (post-RT) FDG PET/CT scans were available. On pre-RT scan, the high FDG uptake region were auto-delineated using several percentage of the maximal standardized uptake value (SUVmax) thresholds, varying from 40% to 70%. On during-RT scan, FDG uptake region is delineated by 40% SUVmax, manual method respectively. With the FDG-positive areas on post-RT images is defined as 80% SUVmax. The overlap fractions (OFs) were calculated between pre-RT scan and during-RT or post-RT scan. Semi-quantitative assessment was used to determine SUVmax and metabolic tumor volume (MTV). The SUVmax changes during-RT representing the radiotherapy (RT) early metabolic response is attainable. Then, a spearman correlation was used to analysis the correlation between percentage changes in SUVmax during-RT and SUVmax-threshold definition volume pre-RT. RESULTS: Of those 7 patients, a total of 16 FDG-PET scans were acquired. 5 patients were received pre-RT and during-RT scan, while 2 of these 5 patients underwent both post-RT scan. 2 patients were received FDG-PET/CT scan pre-RT and post-RT. The pre-RT scan threshold delineations of 50% SUVmax had a large OF with the 40% SUVmax threshold and manual method delineation on the during-RT scan, 74.3% and 84.4%, respectively. Comparably, the 80% SUVmax on the post-RT scan also largely corresponded (OF > 72%) with the 50% SUVmax threshold and the volume was small compared to the gross tumor volume (GTV), accounting for 29.4%. However, the 50% SUVmax threshold was not correlate with the percentage change in SUVmax (P > 0.05). CONCLUSIONS: A pre-RT FDG-PET scan allows for the identification of during- and post-RT FDG uptake locations. The volume defined by 50% SUVmax may be a suitable threshold for dose escalation.
BACKGROUND: To investigate whether during/post-radiotherapy FDG uptake locations within tumors is likely identified using a pre-radiotherapy scan for non-small cell lung cancer (NSCLC), ultimately enabling confirm that a suitable metabolically active sub-volume pre-radiotherapy of the primary tumor for radiation boosting target. METHODS:Patients with a pathologically proven inoperable stage II-III NSCLC were enrolled. For each patient, one pre-radiotherapy (pre-RT) plus one following 40Gy during-radiotherapy (during-RT) or post-radiotherapy (post-RT) FDG PET/CT scans were available. On pre-RT scan, the high FDG uptake region were auto-delineated using several percentage of the maximal standardized uptake value (SUVmax) thresholds, varying from 40% to 70%. On during-RT scan, FDG uptake region is delineated by 40% SUVmax, manual method respectively. With the FDG-positive areas on post-RT images is defined as 80% SUVmax. The overlap fractions (OFs) were calculated between pre-RT scan and during-RT or post-RT scan. Semi-quantitative assessment was used to determine SUVmax and metabolic tumor volume (MTV). The SUVmax changes during-RT representing the radiotherapy (RT) early metabolic response is attainable. Then, a spearman correlation was used to analysis the correlation between percentage changes in SUVmax during-RT and SUVmax-threshold definition volume pre-RT. RESULTS: Of those 7 patients, a total of 16 FDG-PET scans were acquired. 5 patients were received pre-RT and during-RT scan, while 2 of these 5 patients underwent both post-RT scan. 2 patients were received FDG-PET/CT scan pre-RT and post-RT. The pre-RT scan threshold delineations of 50% SUVmax had a large OF with the 40% SUVmax threshold and manual method delineation on the during-RT scan, 74.3% and 84.4%, respectively. Comparably, the 80% SUVmax on the post-RT scan also largely corresponded (OF > 72%) with the 50% SUVmax threshold and the volume was small compared to the gross tumor volume (GTV), accounting for 29.4%. However, the 50% SUVmax threshold was not correlate with the percentage change in SUVmax (P > 0.05). CONCLUSIONS: A pre-RT FDG-PET scan allows for the identification of during- and post-RT FDG uptake locations. The volume defined by 50% SUVmax may be a suitable threshold for dose escalation.
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