In 1980, a 65-year-old pediatrician I know learned he had colon cancer.

A section of his colon was removed in the same sort of surgery President Reagan had last year. Three years later, this physician learned that his cancer had not only returned but spread to a vital organ, his liver. With conventional drug treatment, he was told, he might have only months to live and no more than a few chances in a hundred of living another five years.

At the National Institutes of Health's Clinical Center in Bethesda, he was told he could participate in a trial of an operation to remove most of his liver. There was perhaps one chance in five of success, he was told, but also the possibility that the operation might hasten his death -- or that he might even die on the operating table.

He decided on the operation. Today, four years later, he is still alive and well with no recurrence so far of the cancer.

"He had a tough decision to make," an NIH doctor says. "We still can't give any guarantees. But he made the right decision -- for him." ::

You as a patient, or perhaps as a "normal volunteer," are asked to take part in a "study" or "research protocol" or "clinical trial."

All are experiments, attempts to learn something science doesn't know. Something about a disease or new drug or what makes us tick.

Scientists can learn some things in test tubes and some things in animals. But animals are not people, and their reactions are often not the same. Only human experiments could give us a polio vaccine, for example, and insulin for diabetes.

In the last 30 years, thousands of American women, volunteering for studies, have helped doctors learn that some gentler procedures are as effective as the most drastic kind of surgery in breast cancer. Many more are still enrolled in such study groups all over the country to try to improve breast cancer treatment.

Should you take part in some kind of study?

The decision, of course, must be personal. There is nothing at all wrong with saying "no," and you should never be denied further care if that is your answer.

But your answer might well be "yes" if: You want to help others who might benefit as a result of this study. You won't be giving up the possibility of some other course, perhaps some other treatment, that might be better for you. You are willing to accept whatever risks, small or large, the study might present.

If you are asked to take part in a study, says Dr. Fernando Cassorla, an NIH investigator, the key things to ask are: "What are the possible benefits? -- to me or others -- and What is the possible harm?"

If a treatment is involved, he advises, "Ask to be told all that is known about its effectiveness, and all that is known about possible side effects.

"There are always side effects, always complications or risks, even if you're just getting stuck with a needle. If someone says, 'There are no possible complications or risks,' that is always wrong."

But the only way medicine can progress is by experiments, by making hypotheses and testing them -- first, to whatever extent possible, in the laboratory and in animals, then in human trials. ::

Dr. John Fletcher, an Episcopal minister and a PhD in ethical studies, is the NIH Clinical Center's chief bioethicist and a leading thinker in the field.

Yes, he says, asking about benefits and risks -- and also getting your "informed consent" -- are very important, "but the most important ethical question to ask about research is, 'Should it be done? Should it be done at all?'

"Researchers fall in love with their work. It's necessary to protect both the patient and the investigator from the pitfalls of a scientist's self-interest or desire for advancement and fame."

The question to ask, then, is: "Has the research been approved by a duly appointed Institutional Review Board?" -- the name in most places for a committee that screens all research projects.

Until 1966, a mere two decades ago, any doctor or scientist could undertake almost any human experiment he wanted (the researcher was virtually always "he" in those years) without anyone else's say-so. He might discuss the project with a top official if there seemed to be great danger. Or he might not.

This led to a series of ethical "mega-disasters," Fletcher points out. One glaring example: a case where a zealous and noted physician injected live cancer cells into healthy patients at a Brooklyn hospital without telling them they were being exposed to cancer.

The surgeon general in 1966 decreed that no federal health research money could go to any institution which did not have a board to review all research for both ethical and scientific merit.

The system is not perfect. Most of a review board's members are colleagues of the investigator. Once started, a project may roll on with little scrutiny.

But no one can any longer legally inject you with cancer cells just to see what will happen. ::

As a possible research subject, you can help protect yourself -- and help insure a successful project -- by carefully reading the "informed consent" document you will be handed.

It is up to you and the investigator alike to try to make sure you are truly informed. The investigator or an associate -- not a nurse or secretary or administrator -- must sit down with you and go over the document to make sure you understand it.

That should not be a mass meeting, a simultaneous session for several subjects, unless it is followed by an unhurried individual session. This should not be a hasty session. Cassorla, who studies children, says, "We often take an hour or even more to talk to the parents and child, and also the youngster alone."

This process has holes too. A zealous investigator may be a persuasive salesman. The investigator's motive -- to get the research done -- may not be the same as your motives. Dr. Jay Katz of Yale University says: "What passes today for disclosure and consent in physician-patient interactions is largely an unwitting attempt by physicians to shape the disclosure process so patients will comply with their recommendations."

Ask for more time if you're not sure about anything. Ask questions. If you're ill or under other pressures, recognize that this may not be a time when you should be making snap decisions.

Studies show that persons who are ill often remember little of what is said during such meetings. Protect yourself, says Fletcher, by having a family member or companion "involved from the start, present during the consent meeting and involved with you in the decision."

If possible, talk the decision over with another doctor you trust, one who has only your interest in view.

Thoughtful decisions, says Fletcher, help patient and investigator by creating trust and a mutual determination to make a project succeed, despite any discomforts or unforeseen problems. ::

Dr. Eugene Robin of Stanford University is among doctors who have been most outspoken in warning us about the pitfalls of being a subject. Yet, he says, "If you can find it in yourself to do so, try to keep an open mind about participating in studies," even those "that may not be of direct benefit to you."

"Many patients feel they are contributing to the betterment of medicine in the long run," Dr. Saul Rosen, the Clinical Center's deputy director, reports. "It's a lot more meaningful to many people than giving some dollars to a cause."

"To contribute to the progress of medicine and the welfare of others can be satisfying," says Robin, "but it is your decision to make."

Dr. Dennis Moritz of Walter Reed Army Medical Center recently wrote a letter to The New England Journal of Medicine saying: "It is easy to forget the sacrifices and decisions we often ask our patients to make in the hope of advancing medical science. The published article can never reflect the harsh reality of repeated venipunctures, arterial sticks, lumbar punctures, central lines, various tubes and other invasive procedures."

"A recent {medical} article is exceptional," he wrote, "in using the following sentence . . . 'We are indebted to the brave patient and his family, whose courage and cooperation made this work possible.' "

Next Week: When to call the doctor.