A major new study of Laetrile, the apricot pit derivative widely promoted as a cancer cure, shows no statisticaly significant evidence that the controversial substance has curative or preventative benefit, scientists at the Sloan-Kettering Cancer Center reported today.
A four-year study of Laetrile's effects on laboratory animals, according to the Sloan-Kettering researchers, "showed no beneficial effects against any of these types of cancer which are formed by transplanting cancers cells into previously non-cancerous animals." The tests also showed that Laetrile was ineffective against cancers induced in mice through the use of cancer-causing chemicals.
At the same time, the scientists reported that Laetrile has not been shown to be harmful when used in conjunction with chemohterapyin the treatment of cancer, and they suggested it might even have a pain-reducing effect, much as a placebo (inert medicament) would.
"After a long and significant series of experiments, it doesn't seem that there is any evidence that Laetrile possesses any biolgical activity with respect to cancer, one way or another," said Dr. Lewis Thomas, president of Sloan-Kettering, one of the nation's leading cancer research centers.
Neverthless, Thomas reiterated his previously stated belief that Laetrile should be put to clinical tests on humans to provide the medical community and the public, once and for all, with data on the substances's effects on humans.
Also, Thomas said, surveys should be made of long-term Laetrile users who have taken the drug to prevent cancer. The tests might reinforce the researchers' conclusions about the uselessness of the substance as a propylactic, he said.
Thomas' recommendations went slightly beyond the conclusions of the research team, which were contained in two manuscripts comprising 90 pages that are to be published in the Journal of Surgical Onoclogy. The researchers concluded that there was no scientific evidence to warrant taking Laetrile to human clinical trial, even though "other considerations" may require tests on human cancer victims.
The "other considerations," according to Thomas and Dr. Robert A. Good, directr of Sloan-Kettering's Cancer Research Institute, are sociologcal and political in nature, and have nothing to do with empirical evidence.
Referring to the four years of laboratory experiments on mice, Thomas said "Normally that would end the matter. But obviously we can't end the matter here because of the great proportion of the public that has been persuaded by a skillful public-relations effort to the effect that Laetrile has magical qualities."
Although the Food and Drug Administration has banned the use of Laetrile in interstate commerce, the substance, which is derived also from peach pits or bitter almonds, has been legalized in Alaska, Indiana, Florida, Arizona, Nevada, Texas and Washington. Pro-Laetrile legislation is pending in another dozen states.
Opponents of the substance frequently cite cases in which cancer victims forgo traditional treatment in favor of Laetrile until it is too late to reverse the effects of the disease. Conversely, Laetrile proponents cite numerous cases in which users have benefited from the substance, and they argue that people should be allowed to ingest anything that has not been proved to be harmful.
The substance has been smuggled to tens of thousands of U.S. users, primarily from Mexico, but the relaxing of state laws has led to domestically produced Laetrile. The FDA inter-not have apricot trees.
The results of the cancer center's study were contained in two reports, one of which showed no beneficial effects of Laetrile against any of 10 different types of cancer.
According to the second manuscript, studies failed to reproduce signs of anti-cancerous effects perviously reported in a controversial study by Sloan Kettering scientist Dr. Kanematsu Sugiura in 1973.
Sugiura's findings, widely quoted by Laetrile proponents, were found to be in error when "blind" tests were run on laboratory mice, according to Dr. Daniel S. Martin, a study team member from the Catholic Medical Center.
"Sugiura continues to believe that Laetrile is not a curative but is a paliative [pain-reducing] agent," the report said. At a news conference at the cancer center, Sugiura acknowledged that he had approved the characterization of his current belief about Laetrile.
Dr. C. Chester Stock, Sloan-Kettering vice president for academic affairs and principal author of the paper, said, "I don't imagine our scientific publication will have any impact on the public. I don't think they pay too much intention to scientific publications."
Good, for his part, said, "As scientists, we are not expert at public relations. You know when 65 per cent of all Americans say the thing they fear most - even above war - is cancer, then you have a tremendously powerful issue here."