Optimal Standardized Uptake Value Threshold for Auto contouring of Gross Tumor Volume using Positron Emission Tomography/Computed Tomography in Patients with Operable Nonsmall-Cell Lung Cancer

Abstract

Purpose: Incorporating 18 F-fluorodeoxyglucose positron emission tomography-computed tomography ( 18 F-FDG-PET/CT) for gross tumor volume (GTV) delineation is challenging due to varying tumor edge based on the set threshold of the standardized uptake value (SUV). This study aims to determine an optimal SUV threshold that correlates best with the pathological tumor size. Materials and Methods: From January 2013 to July 2014, 25 consecutive patients of operable nonsmall-cell lung cancer (NSCLC) who underwent staging 18 F-FDG-PET/CT before surgical resection were included in the test cohort and 12 patients in the validation cohort. GTVs were delineated on the staging PET/CT by automatic delineation using various percentage threshold of maximum SUV (SUVmax) and absolute SUV. The maximum pathological tumor diameter was then matched with the maximum auto-delineated tumor diameter with varying SUV thresholds. First-order linear regression and Bland–Altman plots were used to obtain an optimal SUV threshold for each patient. Three radiation oncologists with varying degrees of experiences also delineated GTVs with the visual aid of PET/CT to assess interobserver variation in delineation. Results: In the test set, the mean optimal percentage threshold for GTV was SUVmax of 35.6%±18.6% and absolute SUV of 4.35 ± 1.7. In the validation set, the mean optimal percentage threshold SUV and absolute SUV were 36.9 ± 16.9 and 4.1 ± 1.6, respectively. After a combined analysis of all 37 patients, the mean optimal threshold was 36% ± 17.9% and 4.27 ± 1.7, respectively. Using Bland–Altman plots, auto-contouring with 40% SUVmax and SUV 4 was in greater agreement with the pathological tumor diameter. Conclusion: Automatic GTV delineation on PETCT in NSCLC with percentage threshold SUV of 40% and absolute SUV of 4 correlated best with pathological tumor size. Auto-contouring using these thresholds will increase the precision of radiotherapy contouring of GTV and will save time.

Total metabolic tumor volume on18F-FDG PET/CT is a game-changer for patients with metastatic lung cancer treated with immunotherapy

“…Besides, in a prospective study by Tibdewal et al including 37 patients with operable NSCLC, MTV delineated with an absolute threshold of SUV of 4.0 correlated best with postoperative pathological tumor size. 29 More recently, the fixed absolute threshold of SUV>4.0 has also been designated as the method of choice in a prospective study by Driessen et al evaluating MTV delineation on lymphoma, requiring the least manual adaptation, allowing a high reproducibility and being observer independent. 30 According to the authors, this threshold should now be used in further studies to reach a consensus standard method.…”

A Prospective Study Comparing Dosimetry between Computed Tomography (CT) based Radiation Planning and Positron Emission Computed Tomography (PET-CT) based Radiation Planning in Treatment of Non-Metastatic Non Small Cell Lung Carcinoma

“…Initial studies incorporating PET into treatment planning have been reported (Kiffer et al, 1998). Some have arbitrarily advocated the FDG-avid volume as the region encompassed by the 50% intensity level relative to the tumor maximum intensity (Arriagada et al, 1991;Le Chevalier et al, 1994), whereas Bradley et al, (2004) and TMH data (Tibdewal et al, 2021) employed the 40% intensity level. Paulino and Johnstone (2004) suggested in an editorial autocontouring all areas with a standardized uptake value (SUV) of 2.5.…”

Machine learning for differentiating lung squamous cell cancer from adenocarcinoma using Clinical-Metabolic characteristics and 18F-FDG PET/CT radiomics

“…Tumor segmentation was executed using AccuContour software (version 3.2, Manteia Medical Technologies Co., Ltd., Xiamen, China). Two experienced nuclear medicine physicians employed a threshold of 40% of the maximum standardized uptake value (SUVmax) to delineate the gross tumor volume (GTV) on PET images, reaching a consensus without prior knowledge of the pathology [ 18 , 19 ]. Concurrently, the contours of the GTV on CT slices were outlined based on the integration of PET and anatomical data from the CT images.…”