Influence of TBI Dose on Idiopathic Pneumonia Syndrome in Pediatric Leukemia

A study sought to evaluate the relationship between total body irradiation (TBI) and other factors in the development of idiopathic pneumonia syndrome (IPS) in pediatric patients undergoing allogeneic hematopoietic cell transplantation (HCT) for acute leukemia. The results were published in International Journal of Radiation Oncology, Biology, Physics.

The researchers assessed the correlation between treatment factors and IPS in 121 pediatric patients with acute leukemia (lymphoblastic, n = 84; myeloid, n = 37), ranging in age from 1 to 21 years (median=12). The study population underwent allogeneic HCT at a single institution with matched sibling (n = 33), single unrelated cord blood (sUCB; n = 57), or double unrelated cord blood (dUCB; n = 31) donor between 2006 through 2019. IPS was defined as pulmonary injury based on clinical symptoms, radiographic evidence, or pulmonary function testing within 100 days of HCT in the absence of concurrent infection.

According to the results, IPS developed in 18% of patients from day 6 to 83 (median=20) after HCT. Factors correlated with IPS included donor type (matched sibling, 12%; sUCB, 12%; dUCB, 35%; all P<0.01), high dose rate TBI (35% vs. 9% for LDR, P<0.01), and lower beam energy (6 MV, 35%; 18/25 MV, 15%; all P=0.04). The results showed that factors except age (hazard ratio [HR]=1.09, P=0.20), and lung compensator (HR=1.8, P=0.17) demonstrated an independent association with IPS.

“TBI dose rate is an important variable in the risk of pulmonary toxicity in children treated with allogeneic HCT. TBI dose rates ≤15 cGy/min reduced the risk of post-transplantation IPS and should be strongly considered as an easily implemented parameter in pre-transplantation TBI-based conditioning,” the researchers concluded.