LOS ANGELES — Dr. O. Carl Simonton, a radiation oncologist who popularized the mind-body connection in fighting cancer and helped push the once-controversial notion into mainstream medicine, has died. He was 66.

Simonton, who founded a cancer care clinic in Pacific Palisades on the west side of Los Angeles in the early 1980s, choked to death June 18 during a meal at his Los Angeles area home in Agoura Hills, said his wife, Karen.

Early in his medical career, Simonton noticed that patients given the same dose of radiation for similar cancers had different outcomes. When he looked into why, he concluded that people who had a more positive attitude generally lived longer and had fewer side effects.

Talking openly about cancer was groundbreaking in the 1970s, as were such Simonton techniques as meditation and mental imagery, said Julia Rowland, director of the National Cancer Institute’s Office of Cancer Survivorship.

“For an oncologist to pioneer a mind-body approach was very provocative at the time, and yet very humane,” Rowland said. “It gave people more of a sense of control over their illness and allowed patients to think differently about their role in the healing process.”

After implementing an early psychosocial oncology program while chief of radiation therapy at Travis Air Force Base in Fairfield in the early 1970s, Simonton founded a cancer counseling and research center in Fort Worth, Texas, that included emotional support as a key component.

His own research indicated that when lifestyle counseling was added to medical treatment for patients with advanced cancer, their survival time doubled and their quality of life improved.

A study by Stanford University and the University of California, Berkeley, researchers concluded in 1989 that women with advanced breast cancer who received emotional counseling lived about twice as long as those who did not.

The study was independent evidence that Simonton’s “whole body” approach to battling the illness made a difference, Dr. David Siegel, a psychiatrist and Stanford professor who wrote the study, confirmed in an e-mail to the Los Angeles Times.

Simonton outlined his “will to live” philosophy of cancer care in “Getting Well Again,” a 1978 book written with his second wife, a psychotherapist then known as Stephanie Matthews-Simonton, and others. It drew on firsthand experience with patients at his Fort Worth cancer care center.

The book was “highly praised” by officials at the National Institutes of Health, and by doctors who specialized in cancer and heart problems, the Times reported in a 1981 article with the headline, “Medicine’s ‘Other Side’ — the Mind.”

Thousands of counselors have trained in the Simonton Method, which includes teaching patients to visualize their bodies fighting cancer cells — and winning the war.