This study will investigate the toxicity, safety and pharmacokinetics of pretargeted radioimmunotherapy with anti-CEA x anti-hapten bispecific antibody TF2 and Lu-177-labeled di-HSG-DOTA peptide IMP-288. Furthermore, the sensitivity of pretargeted imaging with In-111-labeled IMP-288 as compared to standard methods of tumor detection, and the preliminary efficacy of the therapy.

Pretherapy cycle with IMP-288 labeled In111.

Inclusion Criteria:

• Patients with CEA expressing advanced colorectal tumors for which no standard treatment is available
• WHO performance status: 0 or 1
• Having normal hematological function: Neutrophils > 1.5 x 109/l; Platelet count > 150 x 109/l, without transfusion during the previous month; Hemoglobin > 5.6 mmol/l
• Total bilirubin < 2 x upper limit of normal (ULN)
• ASAT, ALAT < 3 x ULN
• Serum creatinine < 2 x ULN
• Cockcroft clearance > 50 ml/min
• Negative pregnancy test for women of child¬bearing potential (urine or serum)
• Age over 18 years
• Ability to provide written informed consent

Exclusion Criteria:

• Known metastases to the brain
• Chemotherapy, external beam radiation or immunotherapy within 4 weeks prior to study. Limited field external beam radiotherapy to prevent pathological fractures is allowed, when unirradiated, evaluable lesions elsewhere are present.
• Prior angiogenesis inhibitors within 4 weeks; bevacizumab within 8 weeks
• Cardiac disease with New York Heart Association classification of III or IV
• Patients who are pregnant, nursing or of reproductive potential and are not practicing an effective method of contraception
• Any unrelated illness, e.g. active infection, inflammation, medical condition or laboratory abnormalities, which in the judgement of the investigator will significantly affect patients' clinical status
• Life expectancy shorter than 6 months.