Impact of hybrid FDG-PET/CT on gross tumor volume definition of cervical esophageal cancer: reducing interobserver variation.

Ryo Toya,Fumi Sakamoto,Yoshinobu Shimohigashi,Natsuo Oya,Noriko Tsuda,Shinya Shiraishi,Tetsuo Saito,Masanori Imuta,Yoshiyuki Fukugawa,Tomohiko Matsuyama,Takahiro Watakabe,Yudai Kai,Yasuyuki Yamashita,Ryuji Murakami,Ayumi Iyama

doi:10.1093/jrr/rrz004

Ryo Toya, Fumi Sakamoto + Show 13 more

Open Access

https://doi.org/10.1093/jrr/rrz004

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Abstract

Intensity-modulated radiation therapy is being increasingly used to treat cervical esophageal cancer (CEC); however, delineating the gross tumor volume (GTV) accurately is essential for its successful treatment. The use of computed tomography (CT) images to determine the GTV produces a large degree of interobserver variation. In this study, we evaluated whether the use of [18F]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET)/CT fused images reduced interobserver variation, compared with CT images alone, to determine the GTV in patients with CEC. FDG-PET/CT scans were obtained for 10 patients with CEC, imaged positioned on a flat tabletop with a pillow. Five radiation oncologists independently defined the GTV for the primary tumors using routine clinical data; they contoured the GTV based on CT images (GTVCT), followed by contouring based on FDG-PET/CT fused images (GTVPET/CT). To determine the geometric observer variation, we calculated the conformality index (CI) from the ratio of the intersection of the GTVs to their union. The interobserver CI was compared using Wilcoxon’s signed rank test. The mean (±SD) interobserver CIs of GTVCT and GTVPET/CT were 0.39 ± 0.15 and 0.58 ± 0.10, respectively (P = 0.005). Our results suggested that FDG-PET/CT images reduced interobserver variation when determining the GTV in patients with CEC. FDG-PET/CT may increase the consistency of the radiographically determined GTV in patients with CEC.

Highlights

Cervical esophageal carcinoma (CEC) is an aggressive tumor that arises in the short segment of the esophagus between the cricopharyngeus and the sternal notch
We evaluated whether the use of fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET)/computed tomography (CT) fused images reduced interobserver variations in determining the gross tumor volume (GTV), compared with the use of CT images alone, in patients with CEC
The mean values of GTV based on CT images (GTVCT) and GTVPET/CT were 30.3 cm3and 22.9 cm3, respectively, for the five observers; GTVPET/CT was significantly smaller than GTVCT (P < 0.001, Table 1)

Summary

Introduction

Cervical esophageal carcinoma (CEC) is an aggressive tumor that arises in the short segment of the esophagus between the cricopharyngeus and the sternal notch. Organ preservation is a common treatment goal for CEC, and radiotherapy (RT), with or without chemotherapy, is the accepted standard of care [1, 2]. The cervical esophagus lies in close proximity to the spinal cord and courses through the lower neck and upper thorax with drastic changes in contour and diameter of the anatomy. Unlike esophageal cancer arising from other subsites, higher RT doses of 60–66 Gy are usually prescribed for CEC treatment [2, 3], but it is difficult to achieve uniform tumor coverage with 3D conformal RT [4]. Intensity-modulated radiation therapy (IMRT), a more modern technique, allows dose escalation to the levels required to improve local control without increasing the toxicity to normal tissues; this RT technique is being increasingly used to improve locoregional control and

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