In this phase I study 6 patients with inoperable colorectal cancer is treated with calcium electroporation to establish safety and efficacy of the treatment.

A total of 6 evaluable patients with inoperable colorectal cancer are expected to be included in the study and the time for inclusion of patients is estimated to be 1-2 years. All patients will have been offered the standard of care and all available alternatives before entering the protocol. Calcium electroporation will not be compared to other means of treatment.

All patients will be treated once, but in case of residual tumor tissue at follow-up, and if the investigator considers it safe, they will be offered re-treatment. A maximum of 3 treatments per patient will be conducted with an interval of minimum 4 weeks. The patients will be followed with regular examinations for 12 months, starting from first treatment day.

Inclusion Criteria:

• Histologically verified colorectal tumor
• Conferred by multidisciplinary team (radiologists, surgeons and oncologists) discussing options possible for the patient, resulting in agreement that an endoscopic treatment with calcium electroporation should be offered to the patient.
• Treatment free interval of minimum 2 weeks.
• Thrombocytes ≥ 50 billions/l, INR >1,2. Medical correction is allowed, e.g. correction of elevated INR by means of vitamin K.
• Performance status ECOG/WHO ≤2
• Both men and women who are sexually active must use safe contraception (contraceptive coil, deposit injection of gestagen, subdermal implantation, hormonal vaginal ring or transdermal patch.)
• Trial subject ≥ 18 years.
• Trial subject must be able to understand the participants' information.
• Signed informed consent. The patients are considered participants in the study after signing of the informed consent.

Exclusion criteria:

• Coagulative disturbance that cannot be corrected
• Pregnancy or lactation (Pregnancy is ruled out in fertile women by an HCG test in a blood sample)
• Concurrent participation in other clinical trials that involve experimental drugs or participation in a clinical trial involving experimental drugs within 4 weeks prior to administration of the drug in this study.
• Treatment with bevacizumab within the last 4 weeks.
• Heavily inflamed colorectal mucus membrane with bleeding or ulcerations.
• Implanted colon stent
• Other clinical disease or previous treatments that make the investigator deem the patient unfit.