Inclusion Criteria:

- Confirmed diagnosis of colorectal cancer, UICC stage II-IV

- Age between 18 (Austria: 19) and 85 years

- No previous malign tumor

- Surgical resection of the tumor if indicated

- (Post-operative) conventional oncological therapy and measurements, or passive
after-care ("best care")

- Follow-up for several years feasible

- Patient gives written consent to use the anonymized date for evaluation

Exclusion Criteria:

- Anal cancer

- Other Iscador® sorts than Qu in the test group

- Other mistletoe preparations in the test group

- Any mistletoe preparation in the control group

- Non-oncological immunomodulating, -stimulating or -suppressive drugs (e.g. Echinacea,
interferons, Polyerga®, BCG, azathioprine). Allowed are approved tumor inhibiting
immuno- or targeted therapies (e.g. bevacizumab, cetuximab) and tumor specific
vaccines

- HIV infection, Aids, organ transplantation

- High-dose systemic glucocorticoids

- Contraindications for Iscador® Qu (allergy against mistletoe, acute inflammatory
disease or fever > 38.5°C, active tuberculosis, hyperthyreosis with not-adjusted
metabolism, primary brain or spinal tumor, brain metastases)

- Known mistletoe intolerance

- Patients participating in another clinical study with non-approved substances