New Treatment Advised for Colon, Rectal Cancer : Medicine: A seven-year study finds that a combination of radiation, chemotherapy and drugs significantly lowers the chance of the disease recurring.

Citing new evidence that a combination of radiation and drugs given after surgery significantly reduces the death rate for patients with advanced rectal cancer, the federal government Wednesday urged physicians to immediately begin offering the treatment to patients.

This treatment “can make a profound difference in the lives of patients and reduce the death and suffering from this kind of cancer,” said Dr. Samuel Broder, the director of the U.S. National Cancer Institute in Bethesda, Md.

The National Cancer Institute based its “clinical announcement” on a seven-year Minnesota study being published today in the New England Journal of Medicine, as well as on unpublished data. The announcement has been mailed to 150,000 physicians.

The 204-patient study found that the combination of radiation and chemotherapy with the drug 5-fluorouracil reduced the five-year recurrence rate of rectal cancer to 41.5%, compared to a 62.7% recurrence rate with radiation therapy alone.

After seven years of follow-up, about 55% of the patients receiving the combined therapy were alive, compared to about 35% of patients who received radiation alone, the report said. Twelve of the 111 patients who died had no evidence of recurrence of cancer.

“This is a major step forward . . . and opens the door to much more accelerated progress,” said Dr. Charles G. Moertel of the Mayo Clinic in Rochester, Minn., one of the authors of the study.

The advance against rectal cancer is one of many recent developments in the battle against colorectal cancer. Together, colon and rectal cancers are among the most common tumors in both men and women.

An estimated 45,500 Americans will develop new cases of rectal cancer in 1991 and 7,500 will die from the disease, according to the American Cancer Society. An estimated 112,000 cases of colon cancer are expected and 53,000 deaths.

Researchers have determined that an underlying genetic susceptibility may be present in the majority of people who develop the cancers and are close to identifying a specific colon cancer gene.

The rectum is the last six inches of the large intestine. Tumors are usually diagnosed through rectal examinations or examinations with a fiberoptic-lighted tube.

Rectal cancer is often debilitating. This is because surgeons usually must remove the entire rectum and much of the large intestine and create a colostomy, an opening for feces to pass through the abdominal wall.

Men with rectal cancer often become impotent after surgery as a result of nerve damage. Recurrences of the tumor are very painful and lead to a “fairly miserable death,” Moertel said.

Before the new study, radiation therapy after surgery had produced some reduction in local recurrence of rectal cancer but had not been shown to improve long-term survival.

All the patients in the Minnesota study had “high-risk” rectal cancer, which had spread to either surrounding tissue or nearby lymph nodes. The typical patient has been follow-up for more than seven years.

After undergoing surgery, the 204 patients were randomly assigned to receive either radiation or a combination of radiation and two medications.

One of the medicines, 5-fluorouracil, is a well-known anti-cancer drug. It is administered through a vein. The other is an experimental oral drug that can cause severe long-term side-effects.

The federal government is not recommending that physicians use the second drug, methyl-CCNU, because subsequent research has shown that the combination of the two drugs is no better than the use of 5-fluorouracil alone.

The radiation and drug treatment start one to two months after surgery and are administered over several months. Side-effects include stomach upset, bone-marrow suppression and, in about 7% of cases, small-bowel obstruction that requires surgery.