The difference between the CTC positivity rate (≥1 CTC / 7.5 mL) in blood samples of tumor-draining veins compared to the CTC positivity rate in peripheral blood. The positivity fraction and CTC number per 7.5 mL in tumor draining veins and peripheral blood samples will be determined by CellSearch.

The tdEV number per 7.5 mL determined from CellSearch images using the ACCEPT software tool and the fraction of tdEVs positive patients (a cut-off threshold will be applied)(de Wit, 2019). 2. The difference between tdEV measurement in the tumor-draining veins and the peripheral blood will be assessed.

The tumor allele frequency measured by the genome-wide mFAST-SeqS assay (Belic, 2015) and the fraction of patients with high tumor allele frequency will be determined. For this, a threshold of 10% tumour allele frequency will be applied to discriminate high allele frequency (>10%) from low allele frequency (≤10%) cases (Belic, 2015; de Wit, 2019). 2. The difference between ctDNA measurement in the tumor-draining veins and the peripheral blood will be assessed.

Correlation of any of the biomarker or in combination with clinical parameters and with patient clinical outcome (OS and RFS)

The number of tumor tissues (primary tumor, lymph node metastasis, biopsy material), isolated CELLSEARCH® CTCs and plasma/ctDNA samples generated from CIRCULATE1 and stored in the respective biobanks from the University Hospital of Cologne and from University Hospital Düsseldorf.

Adenokarzinome des Ösophagus und des gastroösophagealen Überganges (AEG I und II)

• histologically proven adenocarcinoma of the GEJ type I and II, resectable, non-metastatic tumor
• age ≥18
• Eastern Cooperative Oncology Group (ECOG) performance status 0-2,
• American Society of Anesthesiologists (ASA) < 4.
• pre-treatment stage cT1N+ M0 or cT2-4a N0/N+, M0 GEJ type I and II adenocarcinomas can be included. In case of stage cT4a, curative resectability has to be explicitly verified by the local surgical investigator prior inclusion.
• Written informed consent and the ability to understand the nature of the study and the study-related procedures and to comply with them has to be ensured.

• tumors of squamous, adenosquamous or other non-adenocarcinoma histology
• patients with inoperable or metastatic GEJ type I and II adenocarcinoma, GEJ type I and II adenocarcinoma staged cT1N0 and cT4b, GEJ type I and II cT4a evaluated as not curatively resectable by the local surgical investigator
• unsigned informed consent