The laetrile debate played to a packed house in the Broadway of scientific discussion yesterday, as did the controversies over genetic engineering and whether social behavior has genetic roots.

The only trouble was that most of the audience had heard all the punch lines before.

Experts on every side of the three issues, which are among the most hotly contested in modern science, exchanged verbal barrages at symposia and press conferences scattered around the American Association for the Advancement of Science annual convention here.

There were no verdicts. Neither were any new facts or figures produced, according to scientists at each session. "No one brings in anything new to these annual ego trips," said a bearded man who asked that his name not be used. "It's just a lot of hoopla for you reporters."

Still, he continued, reporters staggered from each meeting laden with research papers and notebooks full of quotations and the issues in the debates got another round of public discussion, and that was all to the good.

Scientists from the National Cancer Institute again told reporters, as they had last September, that a shipment of Mexican-made laetril, the alleged anti cancer drug, had been found to be weak, inconsisten from sample to sample and contaminated. They said again that all study to date has found it useless in treating cancer, but reiterated their willingness to examine any proof to the contrary.

An estimated 50,000 persons got laetrile treatment for cancer in the United States last year, said Dr. Philip Schein, chief of medical oncology at Georgetown University's Cancer Research Center, and that made it "a major social and medical problem."

Meanwhile, a group called the Coalition for Responsible Genetic Research petitioned Congress to extend and tighten federal guidelines for research on the recombinant DNA, the genetic material governing the form and structure of all life.

A Roman Catholic nun, Sister Ann Neale of the U.S. Catholic Conference, urged that researchers be guided by ethical considerations rather than utilitarian ones in deciding whether to proceed with altering genetic patterns in living creatures. No one disagreed, at least in public.