Inclusion Criteria:  Cancer located in oesophagus and/or cardia. Candidate for intended curative surgery. Age > 18 years.  Exclusion Criteria:  Known inherited bleeding disorder. Unable to provide informed consent. Arterial or venous thromboembolic events within the last three months. On-going anticoagulant treatment (Vitamin K antagonists or direct oral anticoagulants). Pregnant or has given birth within the last three months. Known allergy to the trial drug Dalteparin (Fragmin®).