In the medical and financial excitement over two promising new cancer treatments, Dr. Judah Folkman's cautionary words - "We have to be careful with expectations" - were largely ignored.

That's too bad, because Folkman is the lead researcher on angiostatin and endostatin, two proteins that have proved dramatically effective against cancerous tumors in mice. But, as researchers so often caution the lay public, mice are not people.Clinical trials on human subjects are at least a year to 18 months off, and, assuming the drugs work in people, production may not take place until several years after the trials. Cancer researchers who have been down this road before say the drugs may not work as expected, may not even work at all or may have unacceptable side effects.

Still, Folkman and other prominent researchers say angiostatin and endostatin appear "very promising," almost giddy optimism in a field accustomed to disappointment. The proteins work by cutting off the blood supply to the tumors. In mice, the tumors shrank and ultimately disappeared.

Folkman's work was known within the field but when it became popularly disseminated the consequences were stunning. The firm that would make and market the drugs, a clearly unprepared Entremed, saw its stock go from $12 to $85 a share, then go down some again. The speculators' wounds will heal. More heartbreaking is the number of cancer patients and their loved ones flooding doctors and research institutes with demands that the drugs be made instantly available.

Our faith in science has become such that we expect certainty when science is nothing if not the study of uncertainty. Consider that the drug thalidomide, banned in 1962 as a medical evil for the birth defects it caused, may return as a treatment for certain diseases of the immune system.

Folkman's findings were not a breakthrough but an outcome of years of painstaking research and study. Maybe he has found a cure; maybe he has only taken another painstaking step. His expert advice stands: "We have to be careful with expectations."