Emil Freireich, a physician-scientist who helped engineer effective treatments for childhood leukemia at a time when the disease was considered a death sentence, an advance that magnified the promise of chemotherapy and was credited with saving tens of thousands of lives, died Feb. 1­­ in Houston. He was 93.

His death was announced by the University of Texas MD Anderson Cancer Center, where Dr. Freireich worked for half a century and where he died. A spokeswoman for the center said that he had covid-19, the disease caused by the novel coronavirus, but that the cause of death has not yet been determined.

Dr. Freireich was a seminal name in the modern history of cancer — an iconoclast who took on patients whose cases other doctors considered hopeless and, by dint of determination, experimentation and more than occasional confrontation, vastly expanded the options for treatment.

“He was a towering figure in oncology, inspiring generations of oncologists and cancer researchers,” Siddhartha Mukherjee, the author of the Pulitzer Prize-winning volume “The Emperor of All Maladies: A Biography of Cancer,” said in an interview.

“He was a visionary in understanding mechanisms by which cancer cells could acquire resistance to single drugs,” Mukherjee observed. “Using his clinical acumen as well as scientific judgment, he was able to combine the most effective medicines to achieve the landmark cure that galvanized the world of cancer.”

Dr. Freireich attributed his fortitude in large part to his upbringing during the Depression in inner-city Chicago, where his widowed immigrant mother labored in a sweatshop and Dr. Freireich was cared for by an Irish maid. “My youth was the story of doing what you need to do to survive,” he once told the Houston Chronicle. “Figuring a way out of the mess you’re in.”

Inspired by his family doctor — one of the few professional men he encountered in his youth — Dr. Freireich enrolled in medical school and entered practice shortly after the end of World War II. The principal treatments for cancer at the time consisted of surgery and radiation. Chemotherapy was in its infancy. Cancer patients were, in many causes, considered lost causes.

These lost causes included the children Dr. Freireich encountered in the leukemia ward at the National Cancer Institute, an arm of the National Institutes of Health located in Bethesda, Md., where he arrived in 1955.

Leukemia is a form of cancer that affects the blood and bone marrow and, uncontrolled, can cause massive hemorrhaging that Dr. Freireich said made the ward resemble a slaughterhouse.

“You cannot imagine how horrible it was,” he told the Chronicle. “These were 3-, 4-, 5-year-old kids bleeding to death, bleeding out of their ears, eyes, nose, skin and bowels, bleeding internally, vomiting blood. It was a parent’s greatest horror.”

Before he could attack the cancer itself, Dr. Freireich had to devise a way of preventing his patients from hemorrhaging. Shuttling from bedside to the laboratory and back, he determined that his leukemia patients lacked sufficient platelets, the disk-shaped components of blood that facilitate clotting. To persuade skeptical colleagues, he mixed healthy platelets from his own blood with blood samples of his patients and demonstrated the effect.

Further complicating the matter were the limitations of platelets found in donated blood, which degrade after 48 hours — long before it was often transfused. “Because blood bank protocol demanded that the oldest blood be used first,” Dr. Freireich told an MD Anderson publication, “the children all along had been getting blood that was too dated to contain platelets.”

Dr. Freireich was credited with patenting the first continuous-flow blood-cell separator, a tool used to remove platelets and other particles from donated blood.

His innovations in the use of chemotherapy proved even more revolutionary. He achieved them with colleagues including one whose name produced one of the more remarkable coincidences of nomenclature. Newly arrived at the National Cancer Institute, Emil Freireich (known to friends as “J”) found himself working side by side with the oncologist Emil Frei III (called Tom).

“If Freireich had been a character in a film, he would have needed a cinematic foil, a Laurel to his Hardy or a Felix to his Oscar,” Mukherjee wrote in “The Emperor of All Maladies.” “Where Freireich was brusque and flamboyant, impulsive to a fault, and passionate about every detail, Frei was cool, composed, and cautious, a poised negotiator.”

Working with other researchers, they upended chemotherapy — and vastly expanded their patients’ life expectancies — by combining as many as four anti-cancer drugs that had previously been used alone.

The immediate effects of the highly toxic drugs were catastrophic, sickening patients at times nearly to death.

“They said I was unethical and inhumane and would kill the children,” Dr. Freireich told an interviewer years later, recalling the reaction of many colleagues who advocated allowing the children to die in peace. “Instead, 90 ­percent of them went into remission immediately. It was magical.”

According to the National Cancer Institute, the five-year survival rate for acute lymphoblastic leukemia — the most common childhood cancer — today stands at 90­ percent for children younger than 15.

Dr. Freireich’s findings about combined chemotherapeutic drugs, for which he, Frei and others shared the 1972 Albert Lasker Clinical Medical Research Award, were applied to treatment for other cancers and are regarded as a turning point in the history of oncology.

Emil J Freireich — the middle initial stood for nothing — was born in Chicago on March 16, 1927. In his family, it was said that his father, who was believed to be German, died in a suspected suicide after the stock market crash of 1929. Dr. Freireich’s mother was from Hungary.

Encouraged by a teacher, Dr. Freireich enrolled in college at 16, financing his education with what to him then was the staggering gift of $25 from a benefactor and the wages he earned waiting tables. He received a medical degree from the University of Illinois College of Medicine in 1949, when he was 22, eventually undertaking a fellowship in hematology.

Dr. Freireich joined MD Anderson in 1965, leading the leukemia research program for decades and serving on the faculty until his retirement in 2015.

Survivors include his wife of 67 years, the former Haroldine Lee Cunningham of Houston; four children, Debbie Freireich Bier of Lyons, Colo., David Freireich of Round Rock, Tex., Lindsay Freireich of Katy, Tex., and Tom Freireich of Austin; six grandchildren; and three great-grandchildren.

Emil Frei III died in 2013.

So great was Dr. Freireich’s ardor in making his case to colleagues that he once reputedly shattered a glass conference table with the pounding of his first. But to his patients’ bedside he brought a gentle touch, comforting them in the throes of chemotherapy with aspirin or a blanket. His daughter Debbie said that he remained in touch with many patients, and the families of those who were lost, for years.