Commonly Prescribed Restrictive Diet May Be Unnecessary Before Autologous Stem Cell Transplantation

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People undergoing a stem cell transplant for cancer do not derive any benefit from a restrictive diet that is commonly prescribed to prevent infections, according to a new trial presented by Stella et al at the 2022 American Society of Hematology (ASH) Annual Meeting and Exposition (Abstract 169). Researchers found that patients who followed the restrictive diet—which allows only foods that have been cooked to about 175°F and forbids fresh fruits and vegetables—did not have significantly lower rates of infection. People on the diet also reported a poorer quality of life compared with those served a standard hospital-prepared diet.

“A protective diet is an unnecessary burden for our patients because it impairs quality of life without reducing infection incidence,” said Federico Stella, MD, of the Università degli Studi di Milano–Istituto Nazionale dei Tumori in Milan, Italy. “I think our results can be practice-changing in the context of autologous stem cell transplantation.”

In a recent survey, 90% of cancer centers reported prescribing a restrictive diet, also called a protective diet or a low-microbial diet, for patients undergoing stem cell transplants in an effort to reduce patients’ exposure to potentially harmful bacteria while their immune system is weak. The new study is the first randomized controlled trial to prospectively test the efficacy of this approach.

Study Details and Results

Researchers enrolled 247 adult patients undergoing stem cell transplantation and randomly assigned half to receive a protective diet and half to receive standard hospital food, which included the option of fresh fruits and vegetables prepared according to safe food-handling procedures, as well as cold cuts and pasteurized honey and yogurt. Participants followed their assigned diet from the start of chemotherapy (administered before a transplant) until their white blood cell count recovered after the procedure. Three-quarters of the patients underwent an autologous stem cell transplant, and the rest underwent an allogeneic stem cell transplant or high-dose induction chemotherapy.

The results showed no significant difference between the two groups on any of the trial’s primary endpoints, including rates of infection and deaths during neutropenia; rates of graft-vs-host disease; feeding outcomes including length of hospitalization, nausea, or need for intravenous nutrition; or adverse events during up to 30 days following autologous transplants and 100 days following allogeneic transplants. About 34% of those on the protective diet and 39% of those on the nonrestrictive diet experienced infections overall. The rates of fever of unknown origin, commonly used as an indicator of infection, were also comparable between groups, occurring in 43% of patients on a protective diet and 39% of those on the nonrestrictive diet.

Those assigned to the standard hospital diet reported higher satisfaction, with 35% of these patients reporting that their “prescribed diet did not negatively impact my alimentation,” compared to just 16% among those assigned to the protective diet.

“The nonrestrictive diet is definitely preferred by patients,” said Dr. Stella. People on the nonrestrictive diet also experienced less weight loss 1 month after their procedure.

The researchers plan to analyze stool samples to investigate possible correlations between diet, microbiome composition, and immune system changes following stem cell transplantation.

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