But in 1990 Dr. Anagnostou published some of the first evidence suggesting that Amgen's then brand-new anemia drug, Epogen, might fuel the growth of tumors. Few people paid heed.

"Many people believed the work I did was not reproducible," recalled Dr. Anagnostou, who was then a blood disease specialist at Brown University. Unable to obtain a federal grant to conduct further studies, he said he eventually moved on to other things.

Now, people are paying more attention. Eight clinical trials have suggested that Epogen and related anemia drugs, widely used to treat the anemia caused by cancer chemotherapy, might make tumors worse or hasten the death of cancer patients.

On Thursday an advisory committee to the Food and Drug Administration will consider placing further restrictions on use of the medicines -Amgen's drugs Epogen and Aranesp, and the Johnson & Johnson drug Procrit.

"The sense is there's some smoke, but we don't know if there's any fire," said David A. Gewirtz, a professor of pharmacology and toxicology at Virginia Commonwealth University. In his study, Dr. Gewirtz found that Epo did not stimulate growth of breast cancer cells in a dish.