Lung Function Predicts Mortality After Stem Cell Transplant

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Pulmonary function tests are often performed before hematopoietic stem cell transplantation to screen for underlying respiratory problems. Recent research has suggested that pretransplant pulmonary function tests—particularly a measurement combining FEV₁ and the diffusing capacity of carbon dioxide (DLCO)—can predict posttransplant respiratory failure and mortality.¹

Jason Chien, MD, and colleagues retrospectively studied the pretransplant pulmonary function and arterial blood gasses of 2,852 cancer patients who received allogeneic stem cell transplants during a 12-year period. FEV₁, FVC, total lung capacity, DLCO, and alveolar-arterial oxygen tension difference (PaO₂) were measured. Patients in the nonmyeloablative group received 2Gy total body irradiation. Those in the myeloablative group received either total-body-irradiation-based or non-total-body-irradiation-based regimens. According to Dr. Chien, an Assistant Professor of Pulmonary and Critical Care Medicine at the Fred Hutchinson Cancer Center, “Assessment of pretransplant pulmonary function tests is very important, given their relationship with mortality risk. We would like to see every transplant center in the world screen their patients with pretransplant pulmonary function tests.”

LOW PULMONARY FUNCTION SPELLS BAD NEWS

The majority of patients (80%) had normal pretransplant pulmonary function tests. Similarly, among the 1,135 patients who had blood gas measurements, 85% had a normal PaO₂. The median PaO₂ was 5.4 mm Hg (range, 0 to 52.9 mm Hg). However, early respiratory failure (defined as respiratory failure that necessitated mechanical ventilation within 120 days after transplant) occurred in 14% of patients—within a median of 21 days. This is important, the researchers pointed out, because 91% of the patients who received ventilation died.

Multivariable analyses revealed that FVC, TLC, and DLCO less than 80%, PaO₂ more than 30 mm Hg, and pretransplant FEV₁ less than 70% were significantly associated with occurence of early respiratory failure after the transplant procedure. A significant increase in mortality was observed when the pulmonary function test values were less than 70% or the oxygen tension difference was above 20 mm Hg. It is possible that “the lungs injured prior to transplant had less reserve, such that the patient [was] unable to compensate for any significant damage to the lungs after transplant,” explained Dr. Chien. Alternatively, he suggested that pulmonary function tests could serve as a “nonspecific measure of the patient’s overall health status.”

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