Inclusion Criteria:

          -  Metastatic colorectal cancer patients for whom conventional therapy has failed;
             defined as 2 lines of chemotherapy including oxaliplatin or irinotecan- containing
             regimens as well as an EGFR inhibitor if applicable.

          -  Tumor lesion suitable for biopsy

          -  Age >18 years

          -  Clinically or radiologically measurable tumor deposits according to the RECIST
             criteria

          -  WHO performance status 0-1

          -  Radiology studies (CT thorax/abdomen/pelvis) and echo cor and ECG must be performed
             within 28 days prior to registration.

          -  Before patient registration in the trial, written informed consent must be given
             according to national and local regulations.

          -  Blood test requirements:

        Neutrophils > 1.0 e9/L Platelets > 75 e9/L Bilirubin < 20 µmol / L. Serum creatinine < 1.5
        x ULN

        Exclusion Criteria:

          -  Co-morbidity including, but not limited to, impaired renal-, liver or bone marrow
             function, that based on the assessment of the treating physician, may preclude the use
             of cyclophosphamide at actual doses.

          -  Known hypersensitivity to the study drug, its metabolites or any excipients in the
             infusion solution.

          -  Psychological, familial, sociological or geographical condition(s) potentially
             hampering compliance with the study protocol and follow-up schedule; those conditions
             should be discussed with the patient before registration in the trial

          -  Pregnant or lactating patients cannot be included.

          -  Clinical evidence of serious coagulopathy. Prior arterial/venous thrombosis or
             embolism does not exclude patients from inclusion, unless patient is considered unfit
             by study oncologist.

          -  Patient not able to give an informed consent or comply with study regulations as
             deemed by study investigator.