The study was published in the January 30, 1999, issue of the British medical journal The Lancet, and compared colon cancer recurrence and survival rates in a group of 254 patients. Of this group, 170 had early colon cancer and 84 had more advanced cancer. Half of each group was randomly assigned to receive either a series of vaccinations following surgery or no further treatment.

Patients in the treatment group were given a series of four vaccinations starting about a month after surgery. The first three vaccinations were made from a mixture of neutralized cancer cells taken from the patient and bacteria to boost the immune system. The fourth, given about six months after the initial series, was a booster containing only cancer cells. Only minor side effects were reported.

During the five-year follow-up period, there were 40 recurrences in the control group and 25 in the vaccinated group. The greatest success with the vaccination group was in patients with stage II disease; the rate of recurrence decreased 61 percent, and the survival rate improved by 50 percent.

No significant improvements were found in patients with stage III colon cancer. The vaccine may be ineffective in these cases because there are too many tumor cells to kill, said Herbert M. Pinedo, MD, one of the study authors and a professor in the Department of Medical Oncology, Vrije University, Amsterdam. However, if the vaccine is given in conjunction with chemotherapy to destroy cancer cells, it may be more effective in treating advanced cancer cases, he added. Dr. Pinedo and his colleagues are planning a study to test this theory.

"This seems to be a substantial advance in treating early stage colon cancer," said Gabriel Feldman, MD, director of prostate and colon cancer for the American Cancer Society. In early stage cancer, also referred to as stage I or stage II, the disease has not spread beyond the bowel. Patients with colon cancer have an excellent survival rate when the disease is caught and treated at an early stage, Dr. Feldman said.

The vaccine?s lack of effectiveness for patients with advanced cancer reinforces the importance of receiving regular colon cancer screenings, added Dr. Feldman. "Unfortunately, the benefits of this vaccine won?t be realized by many patients because they don?t receive treatment early." Only about 40 percent of colon cancer cases are discovered in stages I or II. An estimated 94,700 new cases of colon cancer will be diagnosed this year in the US.

If additional studies confirm the vaccine?s effectiveness, the treatment could receive approval from the US Food and Drug Administration and be available to physicians and their patients by the year 2001, Dr. Feldman estimated.

• Colon and Rectum Cancer