ESTRO 2025 - Abstract Book

S901

Clinical - Haematology

ESTRO 2025

Hui C, Simiele E, Lozko Y, et al. Volumetric modulated arc therapy total body irradiation improves toxicity outcomes compared to 2D total body irradiation. Front Oncol. 2024 Sep 16; 14: 1459287. doi: 10.339/ fonc.2024.1459287.

2506

Digital Poster Outcomes of two or more hematopoietic stem cell transplantations with total body irradiation for hematologic malignancies Keiko Nemoto Murofushi 1 , Yuho Najima 2 , Satoshi Kito 1 , Emi Handa 1 , Yumi Ogoshi 1 , Kentaro Taguchi 1 , Sara Hayakawa 1 , Kei Ito 1 , Takuya Shimizuguchi 1 , Noriko Doki 2 1 Radiation oncology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Tokyo, Japan. 2 Hematology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, Tokyo, Japan Purpose/Objective: To evaluate the outcomes of patients with hematologic malignancies who underwent two or more hematopoietic stem cell transplantations (HSCTs) with total body irradiation (TBI) for graft failure or relapse. Material/Methods: Out of 877 patients who received TBI at our institution between January 2013 and May 2023, we retrospectively analyzed 37 patients who received TBI two or more times and exceeded a cumulative dose of 12 Gy. TBI was performed using either two-dimensional radiotherapy (2DRT) or intensity-modulated radiation therapy (IMRT). During 2DRT, blocks of lead were used to shield the lenses, lungs, and kidneys, whereas in IMRT, dose constraints were applied to reduce the dose to these organs. For HSCT with myeloablative conditioning, a total dose of 12 Gy was administered in six fractions, and for HSCT with reduced-intensity conditioning, 3–4 Gy was administered in two fractions. Results: The median follow up period was 8.1 months (range: 0.4–96.5 months). The median age at the first TBI was 42 years (range: 18–57 years). Twenty patients had acute lymphoblastic leukemia, 11 had acute myelogenous leukemia, and 6 had other hematologic malignancies. Thirty-one patients underwent TBI twice, and the remaining six three times. The first, second, and third IMRT TBI sessions were performed in 19, four, and three patients, respectively, and with 2DRT in 18, 33, and three patients, respectively. The median cumulative total dose was 16 Gy (range: 14–24 Gy), with median doses of 12, 4, and 4 Gy in the first, second, and third sessions, respectively. The 1- and 2-year overall survival rates, and non-relapse mortality rates, were 75.7% and 48.6%, and 34.3% and 49.7%, respectively. Grade 3 or higher acute adverse events and acute graft-versus-host disease were observed in 15, 19, and five patients, and 19, 16, and two patients after the first, second, and third HSCT, respectively. No serious late adverse events were observed in the lenses, lungs, kidneys, or liver after the first HSCT. However, after the second HSCT, grade 4 chronic kidney disease (CKD) was observed in three, non-infectious pulmonary toxicity in one, and diffuse alveolar damage in one patient. After the third HSCT, grade 4 CKD grade 4 creatinine elevation, and non-infectious pulmonary toxicity were observed in one patient each.