Impact of 18F-FDG-PET/CT on the identification of regional lymph node metastases and delineation of the primary tumor in esophageal squamous cell carcinoma patients

Stefan Münch,Benedikt Feuerecker,Lisa Marr,Rickmer Braren,Stephanie E Combs,Hendrik Dapper,Marciana-Nona Duma

doi:10.1007/s00066-020-01630-y

Abstract

PurposeIn patients undergoing chemoradiation for esophageal squamous cell carcinoma (ESCC), the extent of elective nodal irradiation (ENI) is still discussed controversially. This study aimed to analyze patterns of lymph node metastases and their correlation with the primary tumor using 18F‑fludeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) scans.Methods102 ESCC patients with pre-treatment FDG-PET/CT scans were evaluated retrospectively. After exclusion of patients with low FDG uptake and patients without FDG-PET-positive lymph node metastases (LNM), 76 patients were included in the final analysis. All LNM were assigned to 16 pre-defined anatomical regions and classified according to their position relative to the primary tumor (above, at the same height, or below the primary tumor). In addition, the longitudinal distance to the primary tumor was measured for all LNM above or below the primary tumor. The craniocaudal extent (i.e., length) of the primary tumor was measured using FDG-PET imaging (LPET) and also based on all other available clinical and imaging data (endoscopy, computed tomography, biopsy results) except FDG-PET (LCT/EUS).ResultsSignificantly more LNM were identified with 18F‑FDG-PET/CT (177 LNM) compared to CT alone (131 LNM, p < 0.001). The most common sites of LNM were paraesophageal (63% of patients, 37% of LNM) and paratracheal (33% of patients, 20% of LNM), while less than 5% of patients had supraclavicular, subaortic, diaphragmatic, or hilar LNM. With regard to the primary tumor, 51% of LNM were at the same height, while 25% and 24% of lymph node metastases were above and below the primary tumor, respectively. For thirty-three LNM (19%), the distance to the primary tumor was larger than 4 cm. No significant difference was seen between LCT/EUS (median 6 cm) and LPET (median 6 cm, p = 0.846)Conclusion18F‑FDG-PET can help to identify subclinical lymph node metastases which are located outside of recommended radiation fields. PET-based involved-field irradiation might be the ideal compromise between small treatment volumes and decreasing the risk of undertreatment of subclinical metastatic lymph nodes and should be further evaluated.

Highlights

Patients with locally advanced esophageal squamous cell carcinoma (ESCC) are usually treated with neoadjuvant chemoradiation and surgery
With regard to the primary tumor, 51% of LNM were at the same height, while 25% and 24% of lymph node metastases were above and below the primary tumor, respectively
PET-based involved-field irradiation might be the ideal compromise between small treatment volumes and decreasing the risk of undertreatment of subclinical metastatic lymph nodes and should be further evaluated

Summary

Introduction

Patients with locally advanced esophageal squamous cell carcinoma (ESCC) are usually treated with neoadjuvant chemoradiation and surgery (nCRT + S). This multidisciplinary approach increases the rate of complete tumor resection, overall survival (OS), and progression-free survival (PFS) compared to surgery alone [1,2,3]. For patients with irresectable tumors or those unfit for or declining surgery, definitive chemoradiation (dCRT) is the recommended treatment of choice [4, 5]. It is obvious that the reduction of longitudinal safety margins and consideration of involved-field irradiation (IFI) requires reliable diagnostic and imaging techniques to identify the primary tumor and metastatic lymph nodes. Because FDG-PET/CT has demonstrated promising sensitivity, specificity, and accuracy regarding the detection of lymph node metastases as well as the detection of the primary tumor [10, 11], implementation of PET into the radiation planning process might change the resulting target volumes, as it has already been demonstrated for other tumor entities like prostate cancer or squamous cell cancer of the tongue [12, 13]

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