Vaccine Increases Cancer-Free Intervals in Stage II Colon Cancer
Dec. 30, 1999 (Cleveland) -- Cancer researchers are expressing cautious optimism about a pair of trials that demonstrate a vaccine made from a patient's own cells may help the body fight off colon cancer recurrences. The latest results come from a group of U.S. researchers who report their findings in the Journal of Clinical Oncology.
The vaccine is given to patients after they have had tumors removed by surgery. Lead researcher Jules E. Harris, who is at Rush-Presbyterian-St. Luke's Medical Center in Chicago, tells WebMD that the vaccine did not improve overall clinical outcome but it did improve the cancer-free time before recurrence. "I would say that in many ways this is a landmark study." Harris says that although the goal is to improve clinical outcome, it is first necessary to achieve longer disease-free intervals and he is confident that this trial has demonstrated the vaccine's ability to do that.
In the study, 412 patients were randomly allocated to be either observed following surgery or to receive the treatment. Patients in the treatment arm received three weekly vaccine injections. Two of the injections contained vaccine made from their own cells that had been treated with radiation and mixed with a virus that works as a vehicle to carry the vaccine to the site of the cancer, and the third shot contained just the irradiated cells. Researchers know that a vaccine is "working" when the patient begins producing antibodies to the cancer.
The study enrolled patients with both stage II (disease limited to the colon) and stage III disease (with spread to lymph nodes), but no patients with stage III disease had a positive response to the vaccine, says Harris. This finding confirms earlier observations that "immunotherapy [therapy using antibodies] is only useful where you have a limited or small tumor burden," he said.
Harris says that a trial by investigators from the Netherlands used essentially the same technique but had more positive results. The Netherlands study, published in 1999 in the journal The Lancet, demonstrates the advantage of vaccine preparation in a single laboratory, says Harris. In his study, the vaccine was prepared in labs at each of the seven participating sites. This is particularly crucial because the vaccine is prepared from cells harvested from the bowel "so the tissue is invariably contaminated with bacteria. Therefore, the issue of sterility is very important." Harris says that researchers have since learned how to safely transport tissue, making it possible to produce vaccine at a regional lab. Producing at a single site, which is now being attempted in European countries, will improve vaccine quality, he said.
Harris said he is confident that the FDA will approve the manufacturing process to produce the vaccine and said that once that approval is obtained, researchers will proceed with trials of this type of vaccine for other solid tumors. "Research is already proceeding using this vaccine for renal [kidney] cell carcinoma as well as for recurrent ovarian cancer," he said.
In terms of colon cancer, Harris said the findings from this study would add impetus to screening efforts. Early detection, he said, means a smaller tumor burden, a condition that is ideally suited to immunotherapy. "If we can demonstrate this efficacy in patients with low tumor burden, the focus on preventive care or early diagnosis will be enormously increased," he said.