Dose-Guided Radiotherapy in Oesophageal Cancer: Managing the Real Dose (DGRT)

Managing the Real Dose: Evaluating the Impact on Gastric Filling on the Delivered Radiation Dose in Gastrooesophageal Junction Tumors

This study will prospectively collect patients undergoing the standard CROSS regimen in the neoadjuvant setting of the treatment for gastro-oesophageal cancer. The investigators will focus on the potential geometric differences between the OAR and target volume on the initial planning CT and on the kilovolt (kV) cone-beam computed tomography (CBCT). They expect a potential difference in the abdominal part of the planned target volume (PTV) and/or gastro-oesophageal junction part. Furthermore, the impact of gastric filling , potential tumor regression and the accuracy of 5 mm PTV margin in the thoracic PTV will be monitored.

Optimal radiotherapy planning and delivery is essential for irradiation of gastro-oesophageal junction tumors. There is a need for individualized radiotherapy delivery to the upper abdomen, because of mobility. Likewise, controlling gastric filling by instructing patients about fluid and food intake before treatment, may contribute to positional reproducibility. There is evidence that missing microscopic disease in treating the clinical target volume (CTV) results in a worse prognostic outcome. The investigators want to evaluate wether positional difference of stomach, with and without fasting prescription, has an impact of the delivered dose. They will focus on the part of the CTV extending in the stomach. The investigators hypothesize that measurement of the dose using verification kilovoltage cone beam CTs will provide information on potential cold/hot spots of dose delivery and monitor potential geometric differences during treatment. This may result in a suboptimal treatment and a reconsideration of matching target volume on soft tissue instead of bony landmarks. The investigators will evaluate the first clinical results with DGRT in patients with esophageal cancer.

No additional intervention besides standard treatment prescription will be added. Investigators foresee daily kV cone beam CT matching (already standard in house). this subgroup of 10 patients will be asked not to eat or drink carbonated fluids three hours before CT simulation and daily treatment

Proportion of patients in which the CTV was not covered (CTV D99, V95, Dmean) with and without different filling status of the stomach in patients treated with neoadjuvant chemoradiotherapy for gastroesophageal cancer

stomach movement evaluation on a weekly cone beam CT during chemo radiotherapy with and without feeding/fluid instructions.

Inclusion Criteria: Histologically proven adenocarcinoma of the gastro-oesophageal junction Age 18 years or older International Union Against Cancer (UICC) T2-4 N0-2 M0, potentially resectable disease treated by the CROSS regimen WHO 0-2 Exclusion Criteria: Thoracic adenocarcinoma/squamous cell carcinoma Palliative treatment for the oesophageal cancer