That made it difficult for the F.D.A. to determine which drug was shrinking the tumors.

It did a separate trial of Erbitux alone, and the drug shrank tumors in 10.5 percent of the patients.

These drugs shrink the tumor and return prolactin levels to normal in approximately 80% of patients.

If drugs cannot shrink the tumor deep inside her head, she may need surgery to remove it.

The new drug, carboplatin, shrank the tumor with few side effects, but Medicare refused to pay the $1,000-a-month cost.

The drug, known as SU11248, shrank tumors by at least half in 21 of the 63 patients treated and stopped tumor growth in 23 others.

Nevertheless, researchers said, there were signs that the drug could shrink tumors and prolong lives.

But since then, prospects have dimmed because studies have indicated that the drug shrinks tumors in only 10 to 20 percent of kidney cancer patients.

The drug shrinks the prostate and makes it easier to urinate.

But the drug did shrink tumors more often than the placebo.