Predicting Esophageal Cancer Borders Using PET-Imaging PEGASUS

In Germany, around 7,100 people develop esophageal cancer every year. The treatment of esophageal cancer depends on the histology in addition to the location and tumor stage. Squamous cell carcinomas are differentiated from adenocarcinomas. Until distant metastases are present in functionally operable patients, the treatment of esophageal cancer includes a curative approach using surgical resection with, depending on the risk profile, neoadjuvant chemotherapy or neoadjuvant radio(chemo)therapy. In patients who are functionally inoperable or who refuse surgery, definitive radio(chemo)therapy is given. While the histopathological frozen section is available for surgical resection to differentiate tumor tissue from healthy tissue in addition to the surgeon's macroscopic impression, this assistance in defining the target volume is missing in radiation oncology. Instead, the target volume definition is based, in addition to the contrast-enhanced CT image, on a pretherapeutic endoscopic marking of the tumor boundaries. This allows the tumor boundaries to be delineated in radiation planning imaging. In order to detect the potential microscopic and lymphonodal tumor spread, a large target volume is necessary as a safety margin to avoid later field edge recurrences. According to the current standard, this safety distance extends 4-5cm in both cranial and caudal directions beyond the actual tumor findings. Due to the close positional relationships in the mediastinum, this procedure leads to radiation exposure and subsequent toxicity to the surrounding risk organs such as the lungs, heart and spinal cord. The aim of the present study is to correlate the preoperative endosonographic and imaging local tumor extension and lymph node involvement with the histopathological tumor extension and, in the case of neoadjuvant treatment, with the treatment response by using modern imaging of the tumor and the tumor microenvironment in patients with operated esophageal carcinoma. Since there cannot be any information about the histological tumor extent as a gold standard in the case of definitive radiotherapy, the data from operated patients obtained in the study are extrapolated to the patient population of definitive radiotherapy. From these data, hypotheses should be generated about which patient (groups) benefit from a reduction in the target volume in the definitive radiotherapy treatment setting and whether modern multimodal imaging is suitable for monitoring the therapy response.