• - Safety and tolerability of 131I-huA33 combined with capecitabine (NCI-CTCAE) [ Time Frame: 13 weeks ]
  

• Pharmacokinetics of 131I-huA33 when combined with capecitabine, measured by blood sample analysis (gamma scintillation); [ Time Frame: 6 weeks ]
  
• Biodistribution of 131I-huA33 when combined with capecitabine measured by gamma camera planar and SPECT image analysis; [ Time Frame: 6 weeks ]
  
• Immune response (HAHA) to 131I-huA33 when combined with capecitabine, measured by blood sample analysis. [ Time Frame: 13 weeks ]
  
• Tumour response (RECIST) to 131I-huA33 when combined with capecitabine, measured with radiological imaging (scans) [ Time Frame: 13 weeks ]
  

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-hu A33 into a vein followed a week later by the treatment infusion of 131I-hu A33. The first infusion will be given as an outpatient but for the second patients will be hospitalised 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 9 weeks and again at 12 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-hu A33, that is 12 weeks from the treatment infusion of 131I-hu A33. Patients will only receive one treatment infusion of 131I hu-A33 antibody.