Means, 71, who lives near Porcupine on the Lakota Sioux Pine Ridge Reservation in South Dakota, told the Rapid City Journal he would not have accepted surgery even if doctors had not told him last month the cancer is inoperable. He said the side effects of radiation and chemotherapy are "unacceptable options."
"I'm not going to hang on to life under those conditions. No way am I going to hang on for that," he said.
Means became a contentious national figure during the 1973 Wounded Knee occupation. He was acquitted of federal charges.
Since then, he has become a successful actor, with 34 movies and TV appearances to his credit, and has continued to be an activist.
"I've told people after I die, I'm coming back as lightning," he said. "When it zaps the White House, they'll know it's me."
Means said he is not afraid of death.
"I'm not going to argue with the Great Mystery," he said. "Lakota belief is that death is a change of worlds. And I believe like my dad believed. When it's my time to go, it's my time to go."