Biological dosimetry after total body irradiation (TBI) for hematologic malignancy patients

Purpose: Biological dosimetry based on scoring chromosomal aberrations in p eripheral lymphocytes was compared to physical dosimetry done for total bod y irradiation (TBI) before bone marrow transplantation (BMT) in patients wi th hematologic malignancies. Patients and Methods: Fifteen patients undergoing TBI were included in the study, A total dose of 12 Gy in 2.5 days was fractionated into 2 or 3 daily doses of 1.8 Gy delivered by a 18 MV linear accelerator (dose rate: 15.8 c Gy.min(-1)). Blood samples were obtained from patients before irradiation a nd after the first fraction of 1.8 Gy, A standard dose-effect curve was est ablished by in vitro irradiation of healthy volunteer lymphocytes. Chromoso mal aberrations were scored by the conventional cytogenetics (CCG) method f or unstable anomalies and by fluorescent in situ hybridization (FISH) for s table anomalies. Results: Healthy donor lymphocytes before irradiation yielded 0.1% dicentri cs and 0.3% translocations of chromosome 4 (Chr. 4), that is 2.5% for the w hole genome. Patients before irradiation had 2% of dicentrics and 1.1% of c hromosome 4 translocations. The biologically estimated dose of the 15 patie nts after exposure to 1.8 Gy was 1.93 Gy (95% CI: 1.85-2.05) according to C CG, and 2.06 Gy (95% CI: 1.75-2.15) by FISH. Conclusion: The dose estimated by biological dosimetry, in this case of hom ogeneously distributed radiation of TBI, agrees well with the absorbed radi ation dose calculated by physical dosimetry, (C) 2000 Elsevier Science Inc.