What Is the Appropriate Clinical Target Volume for Esophageal Squamous Cell Carcinoma? Debate and Consensus Based on Pathological and Clinical Outcomes

Abstract

Accurate delineation of clinical target volume (CTV) is critical in the effective management of squamous cell carcinoma (SCC) of esophagus using radiation therapy. Accurate delineation may improve the probability of local control and reduce the risk of complications. However, there are no consistent standards on the proper size of the margins added to the gross tumor volume (GTV). Different institutions and radiation oncologists have discordant opinions. In this paper, we review pathological and clinical outcomes to determine the most appropriate CTV for squamous cell carcinomas (SCC) of esophagus. The CTV for esophageal carcinoma should ensure that all subclinical lesions are encompassed regardless of the physical distance. The most precise method for delineating a reasonable CTV is to combine advanced imaging techniques, such as PET/CT and EUS, which allows the detection and prediction of subclinical lesions based on tumor characteristics such as the pathological type, differentiation, T disease, length and lymph node status.

Keywords: clinical target volume; esophageal squamous cell carcinoma; radiation therapy.

Figure 1

Treatment planning simulated with FLT and FDG positron emission tomography (PET)/computed tomography (CT) for a 72-year-old male patient with upper thoracic esophageal SCC. a. FLT PET/CT image based 7-beam IMRT irradiation field including primary tumor and prophylactic supraclavicular nodes region (SUV=1.4, L_Tumor=4.68 cm, GTV=15.95 cm³, PTV=650.33 cm³),B. FDG PET/CT image based 7-beam IMRT irradiation field including primary tumor and prophylactic supraclavicular nodes region (SUV=2.5, L_Tumor=5.1 cm, GTV=17.19 cm³, PTV=708.21 cm³). The difference between FLT and FDG PET/CT induced GTV is only 1.24 cm³, while that's of PTV is 57.88 cm³. It has shown that with even with a little larger GTV, will affect the PTV significantly, and also will influence organ-at-risk (OAR) as a induced result. (Cited from reference 22, with permission by Elsevier.)

Figure 2

Rate of LNM to different regions according to the location of the primary tumor (Cited from reference 29, with permission by Elsevier.)