Convinced of such benefits and that patients have a right to know, the California Assembly just passed a bill to require that health care providers give complete answers to dying patients who ask about their options. The bill now goes to the state Senate.

Some doctors' groups are fighting the bill, saying it interferes with medical practice. But at an American Society of Clinical Oncology conference in Chicago earlier this month, where the federally funded study was presented, the society's president said she was upset at its finding that most doctors were not having honest talks.

"That is distressing if it's true. It says we have a lot of homework to do," said Dr. Nancy Davidson, a cancer specialist at Johns Hopkins University in Baltimore.

Doctors mistakenly fear that frank conversations will harm patients, said Barbara Coombs Lee, president of the advocacy group Compassionate Choices.

"Boiled down, it's 'Talking about dying will kill you,'" she said. In reality, "people crave these conversations, because without a full and candid discussion of what they're up against and what their options are, they feel abandoned and forlorn, as though they have to face this alone. No one is willing to talk about it."

The new study is the first to look at what happens to patients if they are or are not asked what kind of care they'd like to receive if they were dying, said lead researcher Dr. Alexi Wright of the Dana-Farber Cancer Institute in Boston.