The cancer victims who filled a Maryland Senate hearing room to overflowing today said they do not know what laetrile is, nor do they know how it works. What they said they do know is that it relieves their cancer symptoms and that they want to be able to use it legally.

The doctors who followed them in testifying said they were not sure what laetrile is either. About all they said they knew about it is that the federal Food and Drug Administration has not said it is an effective cancer treatment. The doctors said the prospect of patients using it instead of orthodox cancer treatment frightens them.

The absence of solid information about laetrile did not prevent today's hearing before the Senate Economic Affairs Committee from developing into one of the most passionate of this year's session. Cancer victims hoping that they have found a form of relief opposed doctors who told them they may be throwing their lives away by taking the substance.

Carolyn Hedden, 35, said she is a victim of breast cancer. "Last fall," she said, "when I went to pick up my baby daughter, the pain under my arm was so bad I cried.

"Right now, I'm supposed to be dying. I'm supposed to be very weak, very sick, and definitely not here today."

In the middle of her testimony, Mrs. Hedden gave evidence of he strength.

Reassuring the committee that, "I'm not going to do anything weird," she crawled under a table to reach the center of a cicle of desks where committee members sit and did a back bend, supporting most of her weight on her right arm.

"I don't know what it is, but I fell fine," she said. "I want to be able to take laetrile without feeling like a criminal.I had pain, and I don't have pain now."

Laetrile is a chemical found in about 2,000 plants and foods, particularly in apricot and peach kernels, according to testimony at the hearing. Chemically, it is known as amygdalin, a substance that decomposes into cyanide.

Its proponents describe it as a vitamin that does not cure cancer, but controls it as insulin controls diabetes. Its opponents say it is a drug whose effects they know little about, since it has never been adequately tested due to its Mexican and European manufacturers' refusal to cooperate with American clinicians.

Laetrile is not illegal in the United States, but its interstate transporation for sale has been banned by the FDA. The ban is now under a court challenge, according to testimony.

"My major concern," about laetrile, testified Dr. Peter Wiernik, head of the clinical program at the Baltimore Cnacer Research Center and a researcher at the National Cancer Institute, "is that patients with potentially curable diseases will deny themselves treatment" through orthodox methods "and ultimately die. And that is a crime in this modern day."

"There is no evidence at all from a scientific standpoint that this drug is helpful," Wiernik said.

The bill under consideration today would forbid hospitals, clinics or the medical society from interfering with a doctor who prescribes laetrile for cancer patients.

"I think the passing of this bill would give this drug a certain standing that it should not have," said Dr. Karl Mech, head of the legislative committee of the state mediczl society. "At least, this committee should not give it - the FDA should."

"It's not illegal now, but there's a shadow" of uncertainty about the status of laetrile, said Sen. Edward T. Hall D-Calvert), sponsor of the bill. He said the measure would eliminate that shadow.

Testimony at the hearing indicated laetrile is available in Maryland at some health food stores and from some pharmacists at a cost of about $1 a tablet.

"I have somewhat of a monopoly (on laetrile sales) in the Baltimore area and I do not want it," testified Robert W. Henderaon, a Baltimore apharmacist who said he supports the bill.

"I don't like going home at night, wondering when some harassment agency might come looking for me," he said, in reference to stories of pharmacists in other states, notably California, whose licenses have been challenged over their distribution of laetrile.