The discovery that important cancer experiments reported in a Ph.D. thesis at Cornell University may have been falsified has led to a major setback in cancer research, a Cornell official said last night.

"Extraordinarily important work" into how healthy cells are transformed into cancer cells may be 90 per cent false, Richard E. McCarty, chairman of Cornell's department of biochemistry, said, adding that the work "had attracted a great deal of attention."

McCarty said that Mark D. Spector, a second-year graduate student, "managed to manipulate" two professors and another graduate student working with him into arriving at "extremely exciting" but apparently contrived research results.

Spector had reported the findings in his Ph.D. thesis and contributed to articles in several prominent journals.

Scientists only began to suspect his findings when other research consistently contradicted the published reports, McCarty said.

"You have somebody like that with an absolutely brilliant mind and you don't question him." McCarty said, adding, "We did question him, but one and a half years afterwards."

Spector first defended his findings, but withdrew from Cornell after meeting with McCarty. He was unavailable for comment yesterday.

Volker M. Vogt, professor of biochemistry, who collaborated with Spector on some of the cancer experiments, said it would take a long time to repeat the work, adding, "It's difficult to repeat results that are in part correct."

"I think we are all going to look a lot more closely over our graduate students' shoulders," McCarty said.