F18] FDG-PET/CT for manual or semiautomated GTV delineation of the primary tumor for radiation therapy planning in patients with esophageal cancer: is it useful?

Franziska Walter,Sabine Gerum,Claudia Andrae,Harun Ilhan,Maximilian Niyazi,Claus Belka,Barbara Zollner,Constanze Jell,Falk Roeder

doi:10.1007/s00066-020-01701-0

Franziska Walter, Sabine Gerum + Show 7 more

Open Access

https://doi.org/10.1007/s00066-020-01701-0

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Abstract

BackgroundTarget volume definition of the primary tumor in esophageal cancer is usually based on computed tomography (CT) supported by endoscopy and/or endoscopic ultrasound and can be difficult given the low soft-tissue contrast of CT resulting in large interobserver variability. We evaluated the value of a dedicated planning [F18] FDG-Positron emission tomography/computer tomography (PET/CT) for harmonization of gross tumor volume (GTV) delineation and the feasibility of semiautomated structures for planning purposes in a large cohort.MethodsPatients receiving a dedicated planning [F18] FDG-PET/CT (06/2011–03/2016) were included. GTV was delineated on CT and on PET/CT (GTVCT and GTVPET/CT, respectively) by three independent radiation oncologists. Interobserver variability was evaluated by comparison of mean GTV and mean tumor lengths, and via Sørensen–Dice coefficients (DSC) for spatial overlap. Semiautomated volumes were constructed based on PET/CT using fixed standardized uptake values (SUV) thresholds (SUV30, 35, and 40) or background- and metabolically corrected PERCIST-TLG and Schaefer algorithms, and compared to manually delineated volumes.Results45 cases were evaluated. Mean GTVCT and GTVPET/CT were 59.2/58.0 ml, 65.4/64.1 ml, and 60.4/59.2 ml for observers A–C. No significant difference between CT- and PET/CT-based delineation was found comparing the mean volumes or lengths. Mean Dice coefficients on CT and PET/CT were 0.79/0.77, 0.81/0.78, and 0.8/0.78 for observer pairs AB, AC, and BC, respectively, with no significant differences. Mean GTV volumes delineated semiautomatically with SUV30/SUV35/SUV40/Schaefer’s and PERCIST-TLG threshold were 69.1/23.9/18.8/18.6 and 70.9 ml. The best concordance of a semiautomatically delineated structure with the manually delineated GTVCT/GTVPET/CT was observed for PERCIST-TLG.ConclusionWe were not able to show that the integration of PET/CT for GTV delineation of the primary tumor resulted in reduced interobserver variability. The PERCIST-TLG algorithm seemed most promising compared to other thresholds for further evaluation of semiautomated delineation of esophageal cancer.

Highlights

Radiation therapy is a cornerstone of the multimodality treatment of locally advanced esophageal cancer [1, 2], either as definitive chemoradiotherapy (CRT) or as preoperative CRT based on randomized controlled trials [3, 4]
The best concordance of a semiautomatically delineated structure with the manually delineated GTVCT/GTVPET/computed tomography (CT) was observed for PERCIST-TLG
We were not able to show that the integration of Positron emission tomography/computer tomography (PET/CT) for gross tumor volume (GTV) delineation of the primary tumor resulted in reduced interobserver variability

Summary

Introduction

Radiation therapy is a cornerstone of the multimodality treatment of locally advanced esophageal cancer [1, 2], either as definitive chemoradiotherapy (CRT) or as preoperative CRT based on randomized controlled trials [3, 4]. The landmark trial RTOG 85–11, which established concurrent CRT as the standard of care for inoperable locally advanced esophageal cancer in the early 90s, had used generous margins for elective nodal irradiation as well as for a tumor bed boost [3]. The CROSS trial establishing the role of neoadjuvant CRT more than a decade later introduced much smaller margins including the GTV without any elective nodal irradiation [4]. Target volume definition of the primary tumor in esophageal cancer is usually based on computed tomography (CT) supported by endoscopy and/or endoscopic ultrasound and can be difficult given the low soft-tissue contrast of CT resulting in large interobserver variability. We evaluated the value of a dedicated planning [F18] FDG-Positron emission tomography/computer tomography (PET/CT) for harmonization of gross tumor volume (GTV) delineation and the feasibility of semiautomated structures for planning purposes in a large cohort

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Conclusion