The aim of this explorative phase II clinical trial is to establish the safety and efficacy of intratumoral influenza vaccine in patients with colorectal cancer, as an additive treatment prior to intended curative surgery.

This is an explorative phase 2 clinical trial which will be conducted in two phases. The aim of this study is to establish the safety and efficacy of treating patients with early colorectal cancer with intratumoral influenza vaccine as a down staging and immune response enhancing treatment prior to intended curative surgery.

The first part of the study will be conducted as a pilot study. Six patients with histologically verified or clinically suspicious sigmoid colon cancer who are planned to undergo curative surgery will be included. Patients will be recruited from the Department of Surgery, Zealand University Hospital after their case has been reviewed by the multidisciplinary team (MDT). Standard treatment involves intended curative surgery within two weeks after the diagnosis. The treatment will be performed within a few days and it will be ensured that the experimental treatment will not lead to a significant delay of intended curative surgery.

If the pilot study finishes without violating any stop rules and without any serious adverse events the second part of the study will be initiated. This will be conducted as a phase 2 study where 24 patients with histologically verified or clinically suspicious sigmoid colon cancer and rectal cancer will be included. Patients will be recruited from the Department of Surgery, Zealand University Hospital after their case has been reviewed by the multidisciplinary team (MDT). Standard treatment involves intended curative surgery within two weeks after the diagnosis. The treatment will be performed within a few days and it will be ensured that the experimental treatment will not lead to a significant delay of intended curative surgery.

Inclusion Criteria:

• Patients must be mentally capable of understanding the information given.
• Patients must give written informed consent.
• Clinically suspected or histologically verified malignant tumor of the rectum or sigmoid colon.
• Tumor described as passable at index endoscopy.
• Men or women aged at least 18 years.
• Case reviewed by MDT (surgery, radiology, oncology). Case considered curable with standard surgical resection.

Exclusion Criteria:

• Highly inflamed gastrointestinal tissue which is ulcerated and bleeding
• Ongoing immunosuppressive treatment.
• Concurrent treatment with an investigational medicinal product.
• Patients with any other clinical condition or prior therapy that, in the opinion of the investigator, would make the patient unsuitable for the study or unable to comply with the study recruitments.
• Advanced tumor stages, clinical UICC stage IV.
• Indication for neoadjuvant chemoradiation or chemotherapy prior to surgery
• Acute surgical resection.
• Pregnancy
• Any previous allergic reaction to influenza vaccine or constituents, egg and chicken proteins, neomycin, formaldehyde or octoxinol-9
• Acute febrile illness
• Acute infectious disease
• Influenza vaccine administered within 30 days before study inclusion

Study protocol and informed consent form will be available upon start of recruitment of patients