A Feasibility Study For Boost Target Delineation Using ¹⁸F-FDG PET/CT In Local Advanced Non-small Cell Lung Cancer

objective Currently, patients with inoperable non-small cell lung cancer (NSCLC) are treated with radiation alone for early-stage disease and with chemoradiotherapy (CRT) for locally advanced disease. However, standard radiotherapy (RT) of NSCLC with 60Gy is associated with a 45% to 50% rate of local recurrence. Improvements in local tumor control can be achieved by escalating the radiation dose, but it also increases the incidence and severity of radiation toxicities. To evaluated whether during/post-radiotherapy FDG uptake locations within tumours is likely identified using a pre-radiotherapy scan for non-small cell lung cancer (NSCLC), and explore the optimal biological sub-volume pre-radiotherapy of the primary tumor for dose escalation. Methods Patients of inoperable stage Ⅱ-Ⅲ NSCLC were enrolled, all of Patients is pathologically proven. For each patient, FDGPET/CT scans were performed at pre-radiotherapy (pre-RT) and following 40Gy during-radiotherapy (during-RT) or post-radiotherapy (post-RT). On pre-RT scan, the region of interests (ROIs) were auto-delineated using the maximal standardized uptake value (SUVmax) thresholds,40%,50%, 60%70%. On during-RT scan, FDG high uptake areas is delineated by 40% SUVmax, manual method respectively. With the FDG-positive regions on post-RT images is defined as 80% SUVmax.Calculation of the overlap fractions (OFs) between pre-RT scan and during-RT or post-RT scan. The SUVmax changes during-RT defined as the radio-sensitivity index. Then, a spearman correlation was used to analysis the correlation between radio-sensitivity index and the volumes of VOIs pre-RT. Results A total of 15 patients were included in our study. A total of 34 FDG-PET scans were acquired. Four patients underwent three FDG-PET scan, one pre-RT, one during-RT and one at the end of RT. Two FDG-PET/CT scan were available for all patients:ten patients were received FDG-PET/CT scan were included as a component of the initial staging and during the course of therapy, five patients were received FDG-PET/CT scan before start of RT and after the end of RT. All of these patients had a clearly distinguishable lesion from the surrounding tissue and FDG avid inflammation. The 50% SUVmax had a large OF with the 40% SUVmax 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 VOI delineated by 50% SUVmax 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 high FDG uptake regions. The 50% SUVmax may be a suitable threshold for dose boosting to a biological target sub-volumes.