2868 - Characterizing Pulmonary Toxicity After Low Dose-Rate AP/PA Total Body Irradiation: A Single-Center Experience
Presenter(s)
E. Shen1, J. Shen2, B. D. Adefres3, K. B. Roberts4, Z. Chen5, D. J. Carlson5, J. Snyder2, S. Seropian6, F. M. Foss7, L. Gowda8, I. Isufi6, and T. J. Robinson5; 1Yale Department of Neurosurgery, New Haven, CT, 2Yale Department of Therapeutic Radiology, New Haven, CT, 3Yale New Haven Hospital, New Haven, CT, 4Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT, 5Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT, 6Department of Internal Medicine (Hematology), Yale University School of Medicine, New Haven, CT, 7Yale University School of Medicine, New Haven, CT, 8Yale Department of Internal Medicine, Section of Hematology, New Haven, CT
Purpose/Objective(s):
Total body irradiation (TBI) is a key component of many allogeneic transplant conditioning regimens for hematologic malignancies. Severe pulmonary toxicity has led many centers to develop inverse-treatment planning based approaches. The benefit of more labor-intensive approaches with respect to patient toxicity remains unclear. Our institution has used a consistent, 2D-based approach for decades, providing an ideal setting in which to investigate rates of transplant-related pulmonary toxicity associated with conventional TBI delivery.Materials/Methods:
Single institution, retrospective analysis of all adult patients (ages 18–79) who underwent TBI-based myeloablative (12 Gy in 8 fractions) or non-myeloablative conditioning (2-6 Gy in 1-3 fractions) as part of allogeneic stem cell transplant for acute lymphoblastic leukemia (ALL) or acute myeloblastic leukemia (AML) between January 2014 and May 2025. All patients were treated using an opposed anterior-posterior (AP/PA) technique delivered in the lateral decubitus position with a nominal 85% lead transmission lung block and dose rate of 6–10 cGy/min except for patients receiving 2Gy in 1 fraction, who did not receive lung blocks. Acute pulmonary toxicities occurring within 90 days of transplantation were graded according to the Common Terminology Criteria for Adverse Events (CTCAE).Results:
A total of 142 adult patients were treated, including 59 myeloablative and 83 non-myeloablative courses of TBI. The 90-day actuarial risk of developing severe pulmonary toxicity (Grade 3–5) was low across the entire cohort (n=19, 13.4%) and did not differ significantly between the myeloablative and non-myeloablative cohorts (n=7, 11.9% vs. n=12, 14.5%; p = 0.65). In both cohorts, patients with severe pulmonary toxicity (Grade 3–5) demonstrated significantly inferior overall survival compared with those who did not develop severe pulmonary toxicity (Grade 0–2) (p < 0.001). Of the 19 cases with severe pulmonary toxicity, 12 were due to confirmed infection and none were attributed to radiation pneumonitis. Two patients (1.4%) died of veno-occlusive disease.Conclusion:
Severe pulmonary toxicity was low in our institutional series using conventional TBI, with no cases directly attributable to radiation. Patients who developed severe pulmonary toxicity had inferior survival in both myeloablative and non-myeloablative conditioning regimens, consistent with prior reports. TBI delivered using an AP/PA technique and limited dose rate with lung shielding at our institution appears comparable in safety to modern inverse-planned approaches.