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

PURPOSE: Biological dosimetry based on scoring chromosomal aberrations in peripheral lymphocytes was compared to physical dosimetry done for total body irradiation (TBI) before bone marrow transplantation (BMT) in patients with 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 cGy x min(-1)). Blood samples were obtained from patients before irradiation and after the first fraction of 1.8 Gy. A standard dose-effect curve was established by in vitro irradiation of healthy volunteer lymphocytes. Chromosomal aberrations were scored by the conventional cytogenetics (CCG) method for unstable anomalies and by fluorescent in situ hybridization (FISH) for stable anomalies. RESULTS: Healthy donor lymphocytes before irradiation yielded 0.1% dicentrics and 0.3% translocations of chromosome 4 (Chr. 4), that is 2.5% for the whole genome. Patients before irradiation had 2% of dicentrics and 1.1% of chromosome 4 translocations. The biologically estimated dose of the 15 patients after exposure to 1.8 Gy was 1.93 Gy (95% CI: 1.85-2.05) according to CCG, and 2.06 Gy (95% CI: 1.75-2.15) by FISH. CONCLUSION: The dose estimated by biological dosimetry, in this case of homogeneously distributed radiation of TBI agrees well with the absorbed radiation dose calculated by physical dosimetry.

[Validation of biological dosimetry in patients conditioned with total body irradiation: conventional cytogenetics and in situ hybridization(FISH)]. / Validation de la dosimétrie biologique chez des patients conditionnés par irradiation corporelle totale: étude cytogénétique conventionnelle et hybridation in situ (FISH).

PURPOSE: Validation of biological dosimetry versus physical dosimetry in malignant haemopathy patients conditioned by total body irradiation (TBI) before bone marrow transplantation (BMT). PATIENTS AND 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. CONCLUSION: 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.

Radiosensitivity of human normal and tumoral thyroid cells using fluorescence in situ hybridization and clonogenic survival assay.

PURPOSE: By using cell survival as a reference, we evaluated the radiosensitivity of human normal and tumoral thyroid cells using of radiation-induced translocations. METHODS AND MATERIALS: Tissue samples were obtained from patients undergoing thyroidectomy. Cell cultures were established, irradiated with 60Co, and metaphases painted using commercial whole-chromosome 4 hybridization probe and pancentromeric probe. The clonogenic survival was assessed by conventional colony forming assay. RESULTS: After irradiation, normal cultured thyroid cells yielded a higher number of translocations than cultures derived from adenomas or thyroid carcinoma. The colony forming assay demonstrated, by way of the mean inactivation dose, a higher survival of thyroid carcinoma and adenoma cells than of normal thyroid cells. This difference between tumoral and nontumoral cells is significant in each method (p = 0.0001), and cannot be explained by apoptosis in irradiated malignant cells. Correlation of the results obtained by both methods is shown by comparing the survival fraction at 2 Gy (SF2) and the percentage of chromosome 4 translocations at 2 Gy. CONCLUSION: These results indicate that the yield of radiation-induced translocations serves as a good and rapid prediction of the intrinsic radiosensitivity of thyroid cells, and that this test could be applied to other tumors.

Biologic dosimetry in thyroid cancer patients after repeated treatments with iodine-131.

UNLABELLED: To estimate a cumulative dosimetric index that reflects the dose to the circulating lymphocytes after repeated treatments with 131I, biologic dosimetry was applied to 18 patients with differentiated thyroid carcinoma and neck relapse or lung metastases. METHODS: Chromosomal aberrations were scored in peripheral blood samples that were obtained before and 4 days after each administration of 3.7 GBq 131I according to two methods, conventional cytogenetics and chromosome 4 painting. RESULTS: The mean dosimetric index was equal to 0.5 Gy by both methods after the administration of 3.7 GBq 131I. Repeated administrations of 131I delivered the same dose each time, resulting in a cumulative dose from 1-3.5 Gy in the patients who had two to seven treatments. However, the estimated dose, based on the number of chromosomal aberrations on Day 4 and, above all, from the third treatment on, was considerably lower than the real dose absorbed by the lymphocytes. This may be linked to the phenomenon of apoptosis, which results in a loss of information during the course of repeated irradiation. CONCLUSION: Both chromosomal painting and conventional cytogenetics underestimate the cumulative dose after repeated 131I treatments. A complementary test measuring apoptosis may improve the dose estimates.

Sequential biological dosimetry after a single treatment with iodine-131 for differentiated thyroid carcinoma.

UNLABELLED: To determine the cytogenetic and genotoxic risk associated with therapeutic exposure to 131I (3.7 GBq) in 50 patients with differentiated thyroid carcinoma, we estimated the dosimetric index that reflects the dose to the circulating lymphocytes on Day 4 and at several time intervals after exposure over a period of 2 yr. METHODS: Chromosomal aberrations were scored in peripheral lymphocytes obtained before and then 4 days, 3 mo, 6 mo, 1 yr and 2 yr after the first administration of 3.7 GBq 131I according to two methods: conventional cytogenetics and chromosome 4 painting. RESULTS: The dosimetric index was 0.52 Gy on Day 4, 0.49 Gy at 3 mo, 0.45 Gy at 6 mo, 0.44 Gy at 1 yr and 0.42 Gy at 2 yr by conventional cytogenetics and 0.47 Gy on Day 4, 0.45 Gy at 3 mo, 0.44 Gy at 6 mo, 0.43 Gy at 1 yr and 0.42 Gy at 2 yr by chromosome 4 painting. We found a decrease in the frequency of chromosomal aberrations between Day 4 and 3 mo after exposure. This may be due to the decrease of lymphocyte counts shortly after 131I administration, which will recover later on. In contrast, the number of anomalies remained constant starting 3 mo after 131I administration. CONCLUSION: These techniques permit retrospective biological dosimetry for up to 2 yr after therapeutic exposure to 131I.

Biological dosimetry in patients treated with iodine-131 for differentiated thyroid carcinoma.

UNLABELLED: Biological dosimetry was applied to 30 patients with differentiated thyroid carcinoma who were treated with 131I (3.7 GBq) to ablate thyroid remnants after surgery or in case of metastases. METHODS: Chromosomal aberrations were scored in peripheral blood samples obtained before and 4 days after the first administration of 3.7 GBq 131I according to two methods: conventional cytogenetics and chromosome 4 painting. This generated a dosimetric index that reflects the dose to the bone marrow. RESULTS: Results of both techniques were in close agreement. The mean dosimetric index at Day 4 was 0.54 Gy (95% CI: 0.45-0.62 Gy) by conventional cytogenetics and 0.48 Gy (95% CI: 0.42-0.61 Gy) by chromosome 4 painting. This dose is 2-4 times higher than that derived from the MIRD estimates. Since blood was drawn at Day 4, this technique underestimates the dose by at least a third. The high dose estimate may be related to the hypothyroid status of these patients at the time of 131I administration, a condition which decreases renal clearance of 131I and thus increases whole-body irradiation. This dose estimate was closely related to whole-body retention of 131I at Day 4. CONCLUSION: These data should be used to estimate the risk due to 131I exposure.

Intrinsic radiosensitivity and chromosome aberration analysis using fluorescence in situ hybridization in cells of two human tumor cell lines.

The survival curves for cells of two human tumor cell lines, HT29 and MeWo, have been defined using a Dynamic Microscopic Imaging Processing Scanner (DMIPS). There are two major differences between these two cell lines: (a) HT29 is more radioresistant than MeWo (surviving fraction at 2 Gy of 74 and 27%, respectively) and (b) HT29 presents a marked multiphasic survival curve with hypersensitivity at low doses (< 0.5 Gy) followed by an increase in radioresistance at higher doses which we have interpreted as "induced radioresistance"; this phenomenon is much less pronounced for the more radiosensitive cell line MeWo. We have now measured in these two cell lines the stable chromosomal aberrations and fragments, with the method of fluorescence in situ hybridization (FISH). We have analyzed chromosome 4, which does not have spontaneous translocations in either of these two cell lines. A dose-effect relationship was studied for radiation doses up to 5 Gy. At all doses, both translocations and breaks are more frequent in the radiosensitive cell line MeWo compared to the radioresistant cell line HT29. The correlation between survival and translocations is different for HT29 and MeWo, thus indicating that another factor(s) may be involved in cell killing in these lines.

The identification and characterization of a novel human differentiation-inhibiting protein that selectively blocks erythroid differentiation.

We have isolated a novel inhibitor of erythropoietic differentiation from the plasma of a patient suffering from idiopathic pure red cell aplasia. This differentiation-inhibiting protein (DIP) specifically blocked the differentiation of human burst-forming unit-erythroid (BFU-E), but not colony-forming unit-erythroid (CFU-E) cells. DIP also blocked the maturation of murine BFU-E cells, but not CFU-E or CFU-granulocyte-macrophage cells, and it inhibited the dimethyl sulfoxide (DMSO)-induced differentiation of Friend murine erythroleukemia cells (FLC) at levels between 10(-10) and 10(-12) mol/L. DIP activity was not detectable in the plasma of normal, healthy subjects. Unlike other known inhibitors of hematopoiesis, DIP appears to directly inhibit erythropoietic differentiation, because it did not affect the proliferation of untreated FLC and it effectively blocked FLC hemoglobinization without affecting the ability of the blocked cells to proliferate. DIP blocked FLC differentiation only when added to the culture medium within 1 hour of inducing the cells with DMSO, suggesting that the protein inhibited an early, but critical, DMSO-induced cellular process. DIP appears to be at least partially responsible for the patient's anemia, and its unique activity suggests a role in the early development of some erythroleukemias.