Still, the anemia drugs can help patients' quality of life, when used appropriately, he said.

The anemia drugs are injected or given intravenously in physicians' offices or dialysis centers.

Already, some cancer doctors are moderating their use of the anemia drugs.

A Congressional committee has begun an inquiry into the marketing and regulation of widely used anemia drugs that have recently raised safety concerns.

But there was not a big outpouring of support for the anemia drugs.

Both companies said they had begun trials that could tell whether the anemia drugs worsen cancer or impair survival.

The anemia drug is erythropoietin, a manufactured version of a natural hormone that stimulates the body to produce red blood cells.

Amgen's anemia drug, the best-selling product developed so far by the biotechnology industry, might have broad new uses, recent studies have found.

The experts called for new warnings on anemia drugs used to boost production of red blood cells.

Whatever happens with sales of its anemia drugs, if Amgen is to remain a fast-growing company it must develop new products.