ESTRO 2022 - Abstract Book

S147

Abstract book

ESTRO 2022

Conclusion Our BH technique results in sufficiently stable breath-holds for proton therapy. The BH proton technique resulted in a lower MHD than the BH photon technique in all patients. In the current cohort, BH proton therapy would have resulted in a clinically significant reduction of ≥ 2% in the life time risk of ≥ grade 4 acute coronary events in the majority of patients.

PD-0171 Lung function after total body irradiation in myeloablative allogeneic stem cell transplantation

X. Wang 1 , J. Mortensen 2 , H. Sengeloev 3 , F. Kjaer-Kristoffersen 4 , P. Meidahl Petersen 5 , L. Specht 5

1 National Cancer Center, Chinese Academy of Medical Science, Cancer Institute and Hospital, Beijing, China; 2 Rigshospitalet, University of Copenhagen, Dept. of Clinical Physiology & Nuclear Medicine, Copenhagen, Denmark; 3 Rigshospitalet, University of Copenhagen, Dept. of Haematology, Copenhagen, Denmark; 4 Rigshospitalet, University of Copenhagen, Dept. of Oncology, Section of Radiotherapy, Copenhagen, Denmark; 5 Rigshospitalet, University of Copenhagen, Dept. of Oncology, Copenhagen, Denmark Purpose or Objective To examine the effect on lung function of technique and fractionation of total body irradiation (TBI) in conditioning for myeloablative allogeneic stem cell transplantation (allo-HSCT). Materials and Methods From 09.2010 to 06.2019 178 patients with acute leukemia had TBI for allo-HSCT. 19 children and 37 pts. without lung function test (LFT) before TBI were excluded. The remaining 122 pts. were divided into three groups treated in consecutive time periods: 22 pts. in Group 1 were treated with 2D technology to a total dose of 11.3 Gy in 3 daily fractions; 49 pts. in Group 2 were treated with 2D technology to a total dose of 12.0 Gy in 6 fractions in 3 days; 51 pts. in Group 3 were treated with 3D technology (step-and-shoot) to a total dose of 12.0 Gy in 6 fractions over 3 days. Both techniques were delivered at extended distance (3.5 – 4.2 m) and with a low dose-rate (0.08 - 0.125 Gy/min). Chemotherapy conditioning was cyclophosphamide 120 mg/kg (TBI-Cy) for myeloid diseases and etopophos (etoposide phosphate) 1800 mg/m2 (TBI-Eto) for lymphoid diseases. No other changes expected to influence LFTs were made to the treatment during that period. Pts. were to have spirometry and hemoglobin corrected diffusion capacity (DLCO) before and 3, 6, and 12 months after TBI. We analyzed pts. with complete data on LFTs before and at 6 and 12 months. Differences between groups were compared by χ 2 test. Results 13, 29, and 31 pts could be analyzed in Group 1, 2, and 3, respectively. There was no significant difference in overall survival between the three groups. Forced vital capacity and forced expiratory volume in the first second showed only insignificant changes at the three timepoints. However, the DLCO declined significantly from before to 12 months after TBI for Group 1, with no indication of recovery, see Figure. The DLCO for Group 2 declined but recovered after 6 months, although still not completely after 12 months, indicating that the finer fractionation led to less lung damage. The DLCO for Group 3 declined less and recovered completely, although compared to Group 2, the difference was not statistically significant, indicating that the 3D technique with a dose variation of ≤ 10 % achieved possibly even better sparing of the lung function.