[Validation of biological dosimetry in patients conditioned with total body irradiation: conventional cytogenetics and in situ hybridization(FISH)].
OBJECTIVE
Validation of biological dosimetry versus physical dosimetry in malignant haemopathy patients conditioned by total body irradiation (TBI) before bone marrow transplantation (BMT).


METHODS
The scoring of chromosomal aberrations in peripheral lymphocytes irradiated in vivo was used to perform the biological dosimetry. The data were compared to those obtained with healthy volunteers' total blood exposed to in vitro irradiation with linear accelerator doses (0.2, 0.5, 0.75, 1, 2, 3, 4 and 5 Gy) for dose-response curves. In experimental animal models, can in vivo and in vitro responses be considered as being the same? All the published human data are based on retrospective dose evaluation with very large uncertainties on the dose precisely delivered to the subject. TBI before BMT was taken as a model where the dose calculation results from the physical method, with homogeneous beam and dose delivered precisely along the entire organism. In vivo response allows us to validate biological dosimetry in 15 adult patients (female + male), before (D = 0 Gy) and after the first fraction of 1.8 Gy, delivered by a linear accelerator (18 MV, dose-rate of 15.8 cGy/min-1). Two methods, conventional cytogenetics (CCG) and fluorescent in situ hybridization (FISH painting) of chromosome 4 were respectively used to analyze the unstable chromosome aberrations and stable chromosome aberrations.


RESULTS
Healthy volunteer lymphocytes, before irradiation, yielded 0.1% dicentrics and 0.3% translocations of chromosome 4, with 2.5% for the whole genome. Patients before irradiation had 2% dicentrics and 11.48% chromosome 4 translocations for the whole genome. In the 15 patients, for a physical dose of 1.8 Gy, the evaluated biological dose was 1.93 Gy (95% CI: 1.85-2.05 Gy) with conventional cytogenetics and 2.06 Gy (95% CI: 1.75-2.15 Gy) with FISH.


CONCLUSIONS
These results, in which the biologically estimated dose is in complete agreement with the dose calculated by physical dosimetry in the homogeneous irradiation model, suggest the validation of biological dosimetry in TBI conditioning.
Dossou
J
J
UPRES EA27-10 Radiosensibilité et radiocarcinogenèse humaine, institut Gustave-Roussy, 39, rue Camille-Desmoulin, 94805 Villejuif, France.
M'kacher
R
R
Bridier
A
A
Girinsky
T
T
Violot
D
D
Légal
J D
JD
Lartigau
E
E
Eschwège
F
F
Parmentier
C
C
D000293:Adolescent; D000328:Adult; D002869:Chromosome Aberrations; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008214:Lymphocytes; D008297:Male; D008875:Middle Aged; D011874:Radiometry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014916:Whole-Body Irradiation
Validation de la dosimétrie biologique chez des patients conditionnés par irradiation corporelle totale: étude cytogénétique conventionnelle et hybridation in situ (FISH).