A combination drug therapy to treat some cases of advanced, postoperative colon cancer has been approved by FDA.

Levamisole, a drug used to eliminate intestinal parasites in animals, was approved for use in combination with the cancer drug fluorouracil for patients who have undergone surgery for stage III colon cancer.

This type of cancer, also called Dukes' C colon cancer, is an advanced colon cancer that has spread to nearby lymph nodes. It is second only to lung cancer as a cause of cancer deaths.

About 21,000 of the 110,000 Americans diagnosed each year with colon cancer have stage III colon cancer. Only about 40 percent survive five years after surgery.

Scientists do not yet understand what makes the levamisole-fluorouracil combination work. But in two large clinical trials sponsored by the National Cancer Institute, use of the combination drug treatment following surgery reduced the death rate by about,one-third and reduced the rate of tumor recurrence by about 40 percent. The therapy has not yet been shown effective for treating other stages of colon cancer.

The most common side effects are nausea, occasional vomiting, headache, diarrhea, sores in the mouth, and lowered blood count.

A blood disorder, agranulocytosis, also has been associated with the treatment and has caused one death among the more than 1,000 patients who received it in the NCI trials. Therefore, patients given this therapy must have regular blood tests.

Fluorouracil has been approved to treat cancer of the colon. rectum, breast, stomach. and pancreas. Levamisole has been used to treat intestinal worms in domestic animals and, until now, has been available in the United States only for veterinary use. Levamisole was synthesized in 1966 and developed as a treatment for parasites by Janssen Pharmaceutica of Beerse, Belgium. It works by paralyzing worms so they are eliminated through the intestines.

The drug began to be studied as a cancer treatment after scientists noted interesting changes in the treated animals.

Levamisole as a treatment for advanced, postoperative colon cancer has been available since May 1989 under FDA's Treatment IND Program (through which promising but still-experimental drugs are released to certain patients under specified conditions) and through NCl's Group C cancer treatment program. More than 4,000 patients with stage III colon cancer have received the combination treatment through these programs.

An NCI-supported clinical trial is being conducted for patients with cancer of the rectum to determine if the benefits seen with the new therapy extend to rectal cancer as well.

Levamisole is manufactured by Janssen Research foundation of Piscataway, N.J. It will be marketed under the trade name Ergamisol.

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