In a breakthrough that could lead to many more cancer cures, a leading cancer scientist has learned to grow each patient's own cancer cells outside the body so that he can test drugs to tell which will be effective.

In advanced cancer of the female ovaries, one of the first cancers to which the method has been applied, he has quadrupled the survival times in patients for whom previous treatments had become ineffective.

The ground-breaking work of Dr. Sydney Salmon of the University of Arizona is being used at the National Institutes of Health in Bethesda, the University of Texas at San Antonio, the Mayo Clinic and other centers. Drs. Israel Vlodavsky and Zvi Fuks of the Hadassah-Hebrew University Medical Center in Jerusalem have begun growing their patients' cancer cells on a plastic matrix made in their laboratory.

"What we have always had to do in cancer chemotherapy," Salmon said in an interview, "is pick the best drug combination or sequence we can by what has worked in the past, on the average."

But every patient's cancer cells are a little different. A drug treatment may work in one patient and not in others. The patient loses valuable time while the tumor grows, and the wrong drugs may cause harmful side effects.

Salmon, head of the University of Arizona Cancer Center in Tucson, described his latest results yesterday to the American Association for Cancer Research, which is meeting here.

He said today's "golden age of antibiotics" rests in large part on individual sensitivity tests: cultures of each infected patient's germs to see which drugs affect them.

"It is my belief," he said, "that cancer can be brought into the same kind of era."

Cancer cells long proved among the hardest to cultivate in the laboratory. In lab dishes, healthy cells multiplied and crowded out the cancer cells, in contrast to what happens in the human body. Not until the 1970s were there many "cells lines." In no case does more than one cancer cell in 1,000 survive and multiply in a lab flask.

In the late 1960s, scientists at a Canadian cancer institute developed several clones, or lines of identical mouse cancer cells, in a lab dishes filled with agar, a soft gel made from ocean algae. They showed a relationship between sensitivity to anticancer drugs in these cultures and in tumorous animals.

This prompted Salmon to try to grow similar human cancer cultures by bringing samples of his patients' cancers into the laboratory. In 1975 he and Dr. Anne Hamburger, then his assistant, first succeeded.

Others had tried. The Arizonans enriched their agar with hormones and vitamins. They crammed a dish no bigger than a silver dollar with a half million cancer cells to find the survivors. Their agar inhibited growth of the ordinary connective tissue cells that had crowded out the cancer cells in other attempts.

Today Salmon can culture cells from 60 to 80 per cent of his patients within 10 days to two weeks in most cancers, including breast and bladder cancer, multiple myeloma (tumors of the bone marrow), melanomas (serious skin cancers), sarcomas (bone and connective tissue cancers) and some childhoold cancers.

He has shown that a drug that works in a patient's cells in the laboratory will work in the patient 65 percent of the time. A drug that doesn't work in the lab will fail 95 percent of the time.

In 35 patients with advanced ovarian cancer, Salmon and Dr. David Alberts have increased average survival from 3 months to 14 months, with some patients living much longer. Salmon says he is seeing remissions in other forms of cancer.

"It will take another five years," he warns, "before we know all the statistics. But I think it is just a matter of time until this method becomes widespread."