MEDICINE / CANCER RESEARCH : Panel OKs Treatment for High-Risk Colon Patients

A third of the approximately 50,000 Americans who die each year from post-surgery recurrences of colon cancer could enjoy longer lives if they received a newly approved chemotherapy technique, a panel of medical experts meeting at the National Institutes of Health said Wednesday.

The 13-member panel endorsed the combined use of two drugs, including one that until recently was used only to deworm livestock, for “high-risk” patients who suffer often fatal relapses following surgery to remove a colon tumor.

In its consensus statement, reached after two days of presentations and debate, the panel hailed the new technique as “provocative.” The treatment involves the use of levamisole, previously used on livestock, in conjunction with 5-fluorouracil, or 5-FU, which has been commonly used to fight cancer for three decades.

By itself, levamisole apparently does nothing to stop or delay the re-emergence of cancer, but it dramatically increases the effectiveness of 5-FU.

A National Cancer Institute-Mayo Clinic study last year showed that when the combination is administered to patients whose cancer has breached the colon wall or spread to the lymph nodes, it “reduces the risk of cancer recurrence by 41% and the overall death rate by 33%,” according to the panel’s report.

The Food and Drug Administration in February approved the use of levamisole for post-surgical therapy on victims of colon cancer.

Panelists conceded that they don’t know why levamisole works, but they maintain that its effectiveness warrants its use as a basic treatment for patients in advanced stages of the disease.

“You’re looking at a major impact,” said panel member Dr. Mark Green, a professor and oncologist at the UC San Diego Medical Center. The panel, he said, considers the levamisole/5-FU treatment a standard therapy that can be recommended to colon patients. “You’ve got to have the drug available.”

Since the February announcement, less than 5% of all patients undergoing surgery for colon cancer have received post-surgical treatment using levamisole, almost all of them in controlled clinical studies, Green said.

Each year, about 110,000 Americans develop cancer of the colon, a lengthy midsection of the large intestine. Approximately 40,000 more will suffer from cancer of the rectum. Together, the two represent the second-most common fatal cancers among Americans, following lung cancer.

Surgery to remove tumor material is the main treatment, and for many doctors the only traditionally recommended treatment. However, about half of the time the cancer has developed sufficiently so that it already has spread via the body’s blood system or lymph nodes, usually causing death.

The panel recommended that for advanced rectal cancer, doctors should begin prescribing joint use of chemotherapy and high-dosage radiation, the latter to prevent local recurrence of the removed tumor.

The panel did not recommend levamisole/5-FU for rectal cases.