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University of Cincinnati Academic Health Center
Publish Date: 06/15/01
Media Contact: AHC Public Relations, (513) 558-4553
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Early Results Encouraging for Colon Cancer Vaccine

Cincinnati--According to a report issued by the American Cancer Society in Atlanta entitled Encouraging Results for Colon Cancer Vaccine, Kenneth A. Foon, MD, professor and director of the French Cancer Institute at the University of Cincinnati (UC) College of Medicine, recently reported encouraging results with a vaccine to treat colorectal cancer. These research findings of Foon's earlier colon cancer vaccine trials were presented at the American Cancer Society's 43rd Annual Science Writers Seminar in California, and are leading to additional, larger clinical trials of the treatment. "All of the patients generated an active immune response to the vaccine, and the clinical results look very promising," said Foon, an author of the cancer vaccine report.

In the first clinical trial, 17 of 23 patients with advanced colon cancer that had spread to other organs showed the vaccine produced an immune system response. In a second trial, all 54 patients who were given the vaccine after traditional surgery to remove the colon cancer had strong immune responses. The second group included 33 patients, who were given simultaneous chemotherapy with a powerful chemo drug called 5-FU, which can hamper immune response. One vaccine recipient, whose cancer had spread to 22 lymph nodes before it was surgically removed, is still alive six years later with no sign of recurrence and another whose cancer had spread to other organs is living with no sign of recurrence five years later.

Foon calls the results "extraordinary" and said a Phase III clinical trial of the vaccine will begin within a few months. Half of the 1400 patients will receive standard chemotherapy. The other half will receive the vaccine in addition to standard chemotherapy. Vaccine recipients will receive booster shots for up to five years to keep the immune system at peak level.

Cancer vaccines work much like traditional vaccines against infectious diseases, in which altered proteins from a "foreign" bacteria or virus are injected to act as antigens. These stimulate the immune system to attack any similar proteins found in the body. The immune system can stage this attack by sending out proteins called antibodies that attach to the antigens, marking them for destruction by other immune system cells.

Colon cancer cells are covered with an antigen called carcinoembryonic antigen (CEA). Normal tissue does not have CEA, but colon cancer cells are covered with it. CEA makes it easier to design a treatment that targets cancer cells only. Since CEA is present in the colon cells of a developing fetus, and disappears as people grow older, the immune system sees it as being what was once a normal antigen and tolerates it. This weak defense means the body won't attack a colon cancer cell as it would first-time-visiting proteins such as a bacteria or virus.

Each antibody produced by the immune system responds to only one specific kind of antigen. Foon's team developed a protein that would attach itself to the CEA idiotype (a greek word meaning "one's own kind") and this causes the body to see the CEA-coated cancer cells as invaders to kill. "A relapse-free survival is the goal," Foon said.

Since CEA is found on many other types of cancer tumor cells, the vaccine may not be limited to colon cancer. The national Radiation Therapy Oncology Group (RTOG) recently directed a new lung cancer trial to test the CEA vaccine and other vaccines, in combination with traditional radiation and chemotherapy, at more than 200 sites across the country and including the Barrett Cancer Center in Cincinnati. RTOG is a federally-funded cancer clinical trials cooperative group that carries out multi-disciplinary research nationwide. "Cancer vaccines target the cancer cells only and in the future may be used to both treat and prevent cancer," Foon said.

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