Capecitabine and 131I-huA33 in Patients With Metastatic Colorectal Cancer

The purpose of this clinical trial is to determine whether it is safe to treat patients with advanced colorectal cancer, with humanised A33 antibody tagged with radioactive iodine (131I-huA33) in combination with chemotherapy (capecitabine).

This clinical trial tests the combination of humanised A33 monoclonal antibody tagged with radioactive iodine 131 (131I-huA33) together with capecitabine chemotherapy in patients with advanced colorectal cancer.

When colorectal cancer has spread to other organs, it is generally considered incurable but with a limited number of treatment options. Colorectal cancer cells express proteins on their surface known as antigens, and one of these is called the A33 antigen. An antibody which targets the A33 antigen was initially developed in the mouse and found to bind to human colorectal cancer cells. Because humans developed immune reactions when given the mouse antibody, an antibody, which is more like normal human antibodies, was developed (humanised A33 antibody). In order to increase its effectiveness, radioactive iodine (131I) has been attached to the antibody so that the antibody can deliver radiation directly to colorectal cancer cells. Previous studies have shown that both the unlabelled humanised A33 antibody as well as the humanised A33 antibody tagged with radioactive iodine can be administered safely to humans with no major allergic reactions. The addition of chemotherapy to radiolabelled 131I-huA33 may result in a treatment that is more effective for the treatment of colorectal cancer than either agent alone.

The purpose of this study is to determine whether it is safe to give humanised A33 antibody tagged with radioactive iodine together with chemotherapy. Different dose levels of radioactive iodine attached to a constant dose of antibody will be given together with a fixed total daily capecitabine chemotherapy dose. Providing humanised A33 antibody tagged with radioactive iodine and chemotherapy is tolerated well without major side effects, the dose of capecitabine chemotherapy given with 131I-huA33 will also be increased in order to determine the highest dose that can be given safely in combination with radio-labelled 131I-huA33. The effectiveness of the treatment combination against advanced colorectal cancer will also be assessed.

Patients with advanced colorectal cancer who have never previously received chemotherapy using capecitabine may be eligible to participate in the study. A total of between 15 and 30 patients are expected to be recruited.

Screening blood tests will be performed to determine eligibility, as well as baseline heart and lung function tests and appropriate scans to measure tumour size and assess radiation within the body. Patients will be given a trace-labelled (small radiation dose) infusion of 131I-huA33 into a vein followed a week later by the treatment infusion of 131I-huA33. The first infusion will be given as an outpatient, but for the second, patients will be hospitalized and confined to a radiation-shielded room until radiation levels fall to safe limits. Oral iodine drops will also be given for 28 days in order to protect the thyroid gland from the effects of radioactive iodine. Capecitabine chemotherapy will be taken orally and will commence at the time of the treatment infusion. Each cycle of capecitabine chemotherapy involves the medication being taken twice per day for a total of 14 days followed by 7 days rest. A total of 4 cycles of capecitabine will be given after the treatment infusion.

Blood samples will be taken just before the treatment infusion and then weekly for 13 weeks. There will be weekly physical examinations until 9 weeks after the treatment infusion and again at 12 weeks. Total study duration is 13 weeks from the trace-labelled infusion of 131I-huA33, that is 12 weeks from the treatment infusion of 131I-huA33. Patients will only receive one treatment infusion of 131I-huA33 antibody.

Eligibility Criteria:
Inclusion Criteria:

* Metastatic colorectal cancer.
* Histologically or cytologically proven colorectal cancer.
* Measurable disease on CT scan with at least one lesion \>/= 2cm diameter (to allow adequate infusion imaging).
* Expected survival of at least 4 months.
* ECOG performance status 0-2.
* Vital laboratory parameters should be within normal range including:

  1. Neutrophils \>/= 1.5 x 10\^9/L;
  2. Platelets \>/= 150 x 10\^9/L;
  3. Serum bilirubin \</= 34 micromol/L;
  4. Calculated creatinine clearance \> 50 ml/min.
* Age \>/= 18 years.
* Able and willing to give valid written informed consent.

Exclusion Criteria:

* Previous treatment with capecitabine.
* Untreated active metastatic disease to the central nervous system (new or enlarging lesions on CT or MRI), or within 3 months of treatment (ie surgery or radiotherapy) for brain metastases.
* Other serious illnesses, eg, serious infections requiring antibiotics, bleeding disorders.
* Liver involvement with metastatic disease \> 50% liver volume.
* Chemotherapy, radiation therapy, or immunotherapy within 4 weeks before study entry (6 weeks for nitrosoureas).
* Previous external beam irradiation except if: (i) it was for standard adjuvant pelvic radiation for rectal cancer; (ii) it was for localised irradiation for skin cancer; or (iii) the sum total of all previous external beam irradiation port areas is not greater than 25% of the total red marrow.
* Previous treatment with a monoclonal antibody or antibody fragment AND a positive huA33 human anti-human antibody (HAHA) titre.
* Concomitant treatment with systemic corticosteroids. Topical or inhalational corticosteroids are permitted.
* Mental impairment that may compromise the ability to give informed consent and comply with the requirements of the study.
* Lack of availability of the patient for clinical and laboratory follow-up assessment.
* Participation in any other clinical trial involving another investigational agent within 4 weeks prior to enrollment.
* Pregnancy or breastfeeding.
* Women of childbearing potential: Refusal or inability to use effective means of contraception.