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.
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.
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.
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.
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.