Iscador Qu as Supportive Treatment in Colorectal Cancer (Union International Cancer Control, UICC Stages II-IV)

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