E. Donnall Thomas, a medical researcher who in 1990 received the Nobel Prize for his decades of work to perfect the bone marrow transplant, a groundbreaking procedure that has saved tens of thousands of patients with leukemia and other diseases of the blood, died Oct. 20 at a hospital in Seattle. He was 92.

His death was announced by the Fred Hutchinson Cancer Research Center in Seattle, a preeminent institute for bone marrow transplants that Dr. Thomas helped found nearly four decades ago. He had heart and lung ailments, said Dottie Thomas, his wife and longtime laboratory technician and research collaborator.

The son of a small-town doctor in rural Texas, Dr. Thomas began his research in the 1950s at a hospital in Cooperstown, N.Y. At the time, there was little hope of survival for those with leukemia and other blood cancers.

The standard treatments — mainly crude chemotherapy to kill cancerous cells — were “fairly god-awful” and rarely drove the disease into remission, said Mark James Levis, a leukemia specialist at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University. But early bone marrow transplants had shown little promise. Dismayed by the procedure’s complexity, most experts considered such transplants a medical dead end.

With help from his colleagues, Dr. Thomas set out to prove other­wise. Today, bone marrow transplants are standard care for leukemia. The procedure also is used to treat lymphoma, multiple myeloma, a number of autoimmune diseases, aplastic anemia and myelofibrosis.

“This year’s Laureates paved the way for transplantation in man,” the Nobel Assembly at the Karolinska Institute in Sweden declared in 1990 when Dr. Thomas and Joseph E. Murray, who performed the first successful kidney transplant, received the Nobel in medicine. Their discoveries, the assembly noted, “are crucial for those tens of thousands of severely ill patients who either can be cured or be given a decent life when other treatment methods are without success.”

Dr. Thomas spent nearly his entire career trying to overcome the inherent difficulties of attempts to save lives by transferring tissue from one human into another.

In his case, that tissue was bone marrow, the spongy material in the center of bones where blood stem cells reside. Those stem cells produce red blood cells, white blood cells and blood platelets.

In leukemia, blood stem cells turn cancerous. Chemotherapy and radiation may kill the cancerous cells, but the treatments leave patients without any healthy cells to continue producing blood.

Doctors may introduce new bone marrow from a donor, but dangers abound. The patient’s body may reject the foreign marrow. Or, in the case of the serious condition known as graft-versus-host disease, the donor cells may attack the patient’s own organs.

In 1956, hoping to avoid such complications, Dr. Thomas conducted the first bone marrow transplant on a leukemia patient using donor cells from the patient’s identical twin.

A major breakthrough came when he showed that exhaustive matching techniques could vastly expand the possibilities of transplants, making them viable for people who are not closely related.

E. Donnall Thomas, who died Oct. 20, in his lab at the Fred Hutchinson Cancer Research Center in Seattle. Dr. Thomas received the 1990 Nobel Prize in Physiology or Medicine for his work on bone marrow transplants. (Susie Fitzhugh)

The Nobel committee also recognized him for his successful uses of drugs to counteract the graft-versus-host reaction and render bone marrow transplants safer.

“He was the first to truly develop a completely revolutionary new type of medicine, one that even today is being modified and used to save thousands of lives,” Levis said, noting Dr. Thomas’s success in “bringing together a huge amount of medical and biological science.”

Edward Donnall Thomas was born March 15, 1920, in Mart, Tex. He often rode on the buggy his father took to house calls.

Dr. Thomas received a bachelor’s degree in 1941 and a master’s degree in 1943, both in chemistry and both from the University of Texas at Austin. When he received a telegram with the news that he had been accepted at Harvard’s medical school, he and his wife sold everything they had to buy train tickets.

After graduating from medical school in 1946, he served for two years in the Army.

Murray, his future co-Nobel laureate, was a colleague during their residencies at a hospital in Boston.

In 1963, after his initial work in Cooperstown, Dr. Thomas moved to Seattle to become the first chief of the oncology division at the University of Washington’s medical school. In 1974, he became director of medical oncology at the Hutchinson center. He stepped down as director of the clinical research division in 1990 and retired in 2002.

At the end of his career, Dr. Thomas was one of three doctors at the Hutchinson center who were sued by the families of five patients who had died years earlier during the testing of a modified treatment for leukemia. The family members claimed that the patients had not been informed of the risks associated with the treatment, according to the Seattle Times, which in 2001 had published a series of articles on the matter.

In 2004, a jury found that all of the patients had given informed consent and that the Hutchinson center was not liable for four of the five deaths. The jury found the center liable for the death of the fifth patient, whose donor bone marrow had been misplaced, according to the Times.

“I think trying very hard to obtain informed consent was our first objective,” Dr. Thomas testified during the trial, according to the Times. “It was a tragedy,” he said of the patient deaths. “It is not what we set out to accomplish.”

Survivors include his wife of 70 years, Dorothy Martin Thomas of Clyde Hill, Wash.; three children, Dr. Edward Donnall Thomas Jr. of Lewistown, Mont., Jeffrey A. Thomas of Mill Creek, Wash., and Dr. Elaine Thomas of Albuquerque, N.M.; eight grandchildren; and one great-granddaughter.

Dr. Thomas shared credit for the Nobel Prize with his research colleagues. In a 2007 interview with the Seattle Post-Intelligencer, he also expressed his gratitude to his early transplant patients.

They “were all in­cred­ibly courageous people,” he said.