Lung function ‘stable’ 3 years after hematopoietic cell transplant in sickle cell disease

Key takeaways:

• When comparing median FEV₁ before vs. 3 years after hematopoietic cell transplant, researchers found similar levels.
• Diffusing capacity of the lungs for carbon monoxide was slightly higher at the 3-year mark.

Patients with sickle cell disease who had non-myeloablative hematopoietic cell transplants had similar or better lung function 3 years later, according to results published in Annals of the American Thoracic Society.

Parker Ruhl

“There is more information available now than ever to counsel individual patients about the risks and benefits of undergoing a curative therapy for people living with sickle cell disease,” Parker Ruhl, MD, MHS, associate director for clinical faculty affairs in the office of intramural research at NIH, told Healio.

“This study shows that having a low-intensity transplant is safe for the lungs of most people with sickle cell disease,” Ruhl continued. “Any individual patient should discuss their own health history with their doctor, but these findings are reassuring that low-intensity transplant is safe for the lungs in this population.”

In a prospective, longitudinal study, Ruhl and colleagues assessed 97 patients (median age, 31.8 years; 42% women) with sickle cell disease undergoing non-myeloablative hematopoietic cell transplant (HCT) to determine whether lung function measures and 6-minute walk distance (6MWD) change 3 years after HCT vs. before the transplant.

Researchers had pulmonary function test data for all 97 patients at baseline (before HCT), 91 patients at year one, 72 patients at year two and 55 patients at year three.

6MWD data was available for 79 patients at baseline, 73 patients at year one, 57 patients at year two and 41 patients at year three.

A larger proportion of patients underwent HLA-matched sibling transplants vs. haploidentical transplants (67% vs. 33%).

When comparing median FEV₁ before vs. 3 years after HCT, researchers found similar levels (2.5 L vs. 2.4 L). This outcome was also true during evaluation of FVC, FEV₁/FVC ratio and total lung capacity between the two time periods.

In contrast, diffusing capacity of the lungs for carbon monoxide (DLCO) was slightly higher at the 3-year mark following HCT vs. before HCT (median, 64.6% predicted vs. 60.5% predicted).

Further, researchers observed a significant estimated 3.7% predicted rise (95% CI, 1%-6.3%) in DLCO 3 years after HCT via generalized estimating equation models adjusted for age and sex.

Between the time before vs. 3 years after HCT, there was also an estimated 25.9 m (95% CI, 6.6-45.2) significant increase in 6MWD.

“I suppose we were pleased to see, if not surprised, that a commonly done test of walking distance showed that patients could walk a median of about 26 meters further 3 years after the transplant than before the transplant,” Ruhl told Healio. “There is also evidence from other studies that heart function may improve after transplant in some patients, so these findings on walk distance may show benefits from the heart, lungs or both after transplant, but further study is needed.”

Percent-predicted FEV₁ and FVC measured at 3 years after HCT did not significantly differ from measures taken before HCT, according to researchers.

“In the future, we will study more patients at medical centers around the country and around the world, to see if there are differences in the results for other patients,” Ruhl told Healio.

“We know that many people living with sickle cell disease in the United States and around the world will not have access to have a transplant or gene therapy, so we will continue to do research on how we can best support their lung health as well,” Ruhl added.

Reference:

• ‘Low-intensity’ blood stem cell transplants for sickle cell appear safe for lung. https://www.nih.gov/news-events/news-releases/low-intensity-blood-stem-cell-transplants-sickle-cell-appear-safe-lung-health. Published Aug. 27, 2024. Accessed Aug. 28, 2024.