Total Body Irradiation – Comparison of Outcome after Various Techniques of Irradiation and Shielding: A Polish Lymphoma Research Group (PLRG) Multicenter Study

Abstract

The aim of the study was to compare the efficiency and side effects of total body irradiation (TBI) performed with various techniques in hematology and radiotherapy centers across the country. Three radiotherapy departments performing TBI and five hematology centers performing hematopoietic stem-cell transplantation (HSCT) responded to invitation to the study. Patients conditioned with TBI before HSCT between 2005 and 2010 irrespective of diagnosis were included. Technique of irradiation, dosage, dose rate and usage of lung and lens shields were recorded and analyzed in the context of occurrence of radiation-induced pneumonitis, lung fibrosis, cataract and localization of the recurrence on relation to shields. Patients in whom follow-up data were not available were excluded from the study leaving 138 subjects for further analysis. Three TBI techniques were analyzed: a pair of AP-PA fields with lung and lens shielding, and two variations of four-field box technique, one with standard lung shielding and electron boosts to supplement the chest dose and the other with lung dose reduction to 11 Gy; both without lens shielding. The total dose was 12 Gy: 4 Gy/fx once daily (lung dose approximately 6 Gy) in the first scheme, in the other two 2 Gy/fx bid with approximate lung dose of 11 and 8.5 Gy, respectively. Pneumonitis within the first 6 months after TBI was reported in 15.2% of patients: in 42% with minimum shielding and in 11.1% with standard shielding (p<0.05), lung fibrosis in 3.6% (2.5 and 10.4%, respectively, ns.). The incidence of pneumonitis did not differ between children and adults. In 12.3% of patients a recurrence within the 1st year after TBI was reported, in two in the brain only, and both had lens shielding. Only one case of cataract was reported in a patient with lens shielding. The purposefulness of lens shields application demands reevaluation as they do not seem to significantly reduce the cataract rate whereas partial shielding of the brain can be associated with isolated CNS recurrence in lymphoma patients. Utilization of TBI techniques with more strict lung sparing is associated with reduced pneumonitis rate and does not jeopardize the outcome.