Feasibility Study Shows Multicenter, Observational Case-Control Study Is Practicable to Determine Risk of Secondary Breast Cancer in Females With Differentiated Thyroid Carcinoma Given Radioiodine Therapy in Their Childhood or Adolescence; Findings Also Suggest Possible Fertility Impairment in Such Patients

Objective: This single-center, observational case-control feasibility study sought to test key elements of a protocol for an eventual long-term international observational case-control study of a larger patient cohort, to evaluate the risk of breast cancer as a second primary malignancy in females with differentiated thyroid cancer (DTC) given radioiodine therapy (RAI) during childhood or adolescence. Patients: Females developing DTC after the Chernobyl accident in Belarus and ≤19 years old at the time of thyroid surgery were enrolled: patients given RAI (n = 111) and controls of similar age not given RAI (n = 90). Results: One case of breast cancer was newly diagnosed among the RAI patients, but none in controls. Patients given RAI significantly less frequently needed 2^nd surgeries than did controls (23%, 26/111 vs. 39%, 35/90, P < 0.05); the main indication for such procedures usually is suspicion of local recurrence. RAI patients appeared to have had more frequent reproductive difficulties than did controls: 78% (87/111) of the former vs. 93% (84/90) of the latter had a history of pregnancy (P < 0.01), and the mean number of pregnancies was 1.5 ± 1.2 in RAI patients vs. 1.9±1.1 in controls (P < 0.05). Most notably, infertility was observed in 23% (26/111) of RAI patients vs. 4% (4/90) of controls (P < 0.01). In conclusion, a international observational case-control study on breast cancer after DTC in patients given RAI vs. not given RAI appears to be feasible. Additional research and everyday clinical attention should be devoted to reproductive function after RAI in young females.

Thyroid Cancer Induction: Nitrates as Independent Risk Factors or Risk Modulators after Radiation Exposure, with a Focus on the Chernobyl Accident

In recent decades, differentiated thyroid cancer (DTC) incidence has been increasing worldwide. The important contributions to this phenomenon of "overdiagnosis" driven by wider use of improved ultrasound systems are amply documented, notwithstanding the "real" carcinogenic effects of ionizing radiation, e.g., from the Chernobyl accident or health care interventions. Less well understood is the role of nitrates - as environmental pollutants, in diet, and in medication - in thyroid carcinogenesis. Increasing exposure to nitrates is associated with rising incidence of esophageal, stomach, bladder, and colon cancers. Recent data suggest that in agricultural areas with higher mean nitrate levels in groundwater, DTC risk is also elevated. Our work in Belarus after Chernobyl has shown that children in districts with high nitrate concentrations in drinking water had significantly higher thyroid cancer incidence after irradiation than did their counterparts in areas with lower nitrate concentrations. Notwithstanding thyroid shielding, increasing use of computed tomography and dental X-rays heightens radiation exposure of the salivary glands in the general population, especially in children and adolescents. When nitrate intake is increased, salivary gland irradiation may potentially result in carcinogenic elevations in plasma nitric oxide concentrations. In conclusion, excess nitrate intake seems to be an independent risk factor for DTC. Additionally, we hypothesize from our data that high nitrate levels modulate the carcinogenic effect of radiation on the thyroid. Cohort studies, case-control studies, or both, are needed to quantify the effects of nitrates on DTC risk in the presence or absence of radiation exposure, e.g., that associated with diagnostic or therapeutic health care interventions.

Improved follow-up of patients with differentiated thyroid carcinoma

Aim: Physicians typically are unaware of the radioiodine uptake (RIU) detection limit (LoD) on scintigrams of differentiated thyroid carcinoma (DTC) patients. We evaluated a novel method to determine LoD as a quantitative upper limit for RIU in negative scans and as a value to contextualize faint visible uptake. Patients, methods: To test whether LoD is related to physicians’ ratings, RIU and LoD were calculated from scintigraphic count statistics for 120 static planar neck scans and were compared with the ratings of five nuclear medicine specialists blinded to patient/ scan characteristics regarding visible cervical uptake. Scans were acquired on days 1 (d1) and 2 (d2) post-administration of 298 ± 30 MBq iodine-131 in 60 consecutive DTC patients after recombinant human thyrotropin (rhTSH) or thyroid hormone withdrawal (THW) (n = 30 each). Results: Indicating good inter-observer agreement, ≥ 4 readers concurred regarding 56 (93.3%) [54 (90.0%)] d1[d2] scans. Seventeen scans from 12 patients received ≥ 3 positive votes; in 15 (88.2%), RIU exceeded LoD. RIU assessed from regions-of-interest over former thyroid beds in scans with ≤ 2 positive votes was typically below the LoD (99/103 scans, 96.1%). In 48 patients with ≤ 2 positive votes in both scans, LoD was a median 0.0094% (0.0050%) in d1(d2) images and was significantly lower (p < 0.01) on early or late scans in 22 euthyroid rhTSH patients versus 26 hypo thyroid THW patients. Conclusion: LoD data obtained by the proposed method closely reflect nuclear medicine specialists’ scan ratings and provide comparators in serial scintigrams, improving diagnostic 131I imaging accuracy in differentiated thyroid carcinoma.

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In the last 60 years dramatically increased the content of nitrates in groundwater due to intensive use of nitrogen fertilizers in agriculture. Research in post-Chernobyl period has shown that a sharp increase in the incidence of thyroid cancer depends not only on the level of thyroid dose, but also on the level of nitrates in groundwater.

Major Factors Affecting Incidence of Childhood Thyroid Cancer in Belarus after the Chernobyl Accident: Do Nitrates in Drinking Water Play a Role?

One of the major health consequences of the Chernobyl Nuclear Power Plant accident in 1986 was a dramatic increase in incidence of thyroid cancer among those who were aged less than 18 years at the time of the accident. This increase has been directly linked in several analytic epidemiological studies to iodine-131 (¹³¹I) thyroid doses received from the accident. However, there remains limited understanding of factors that modify the ¹³¹I-related risk. Focusing on post-Chernobyl pediatric thyroid cancer in Belarus, we reviewed evidence of the effects of radiation, thyroid screening, and iodine deficiency on regional differences in incidence rates of thyroid cancer. We also reviewed current evidence on content of nitrate in groundwater and thyroid cancer risk drawing attention to high levels of nitrates in open well water in several contaminated regions of Belarus, i.e. Gomel and Brest, related to the usage of nitrogen fertilizers. In this hypothesis generating study, based on ecological data and biological plausibility, we suggest that nitrate pollution may modify the radiation-related risk of thyroid cancer contributing to regional differences in rates of pediatric thyroid cancer in Belarus. Analytic epidemiological studies designed to evaluate joint effect of nitrate content in groundwater and radiation present a promising avenue of research and may provide useful insights into etiology of thyroid cancer.

Bone mineral density in treated at a young age for differentiated thyroid cancer after Chernobyl female patients on TSH-suppressive therapy receiving or not Calcium-D3 supplementation

Long-term management of patients with differentiated thyroid cancer (DTC) commonly includes TSH-suppressive therapy with L-T4 and, in case of postsurgical hypoparathyroidism, Calcium-D3 supplementation, both of which may affect skeletal health. Experience with female patients treated for DTC at a young age and who were then receiving long-term therapy with L-T4 and Calcium-D3 medication is very limited to date. This cross-sectional study set out to investigate effects of Calcium-D3 supplementation and TSH-suppressive therapy on bone mineral density (BMD) in 124 young female patients treated for DTC at a mean age of 14 years and followed-up for an average of 10 years. BMD was found to be significantly higher in patients receiving Calcium-D3 medication than in patients not taking supplements. The level of ionized calcium was the strongest factor determining lumbar spine BMD in patients not receiving Calcium-D3 supplementation. Pregnancy ending in childbirth and HDL-cholesterol were associated with a weak adverse effect on spine and femoral BMD. No evidence of adverse effects of L-T4 and of radioiodine therapies on BMD was found. We conclude that Calcium-D3 medication has a beneficial effect on BMD, and that TSH-suppressive therapy does not affect BMD in women treated for DTC at young age, at least after 10 years of follow-up.

Prognostic value of positron emission tomography-assessed tumor heterogeneity in patients with thyroid cancer undergoing treatment with radiopeptide therapy

INTRODUCTION

Peptide receptor radionuclide therapy (PRRT) is a treatment option for both iodine-refractory differentiated and advanced medullary thyroid cancer (TC). It requires over-expression of somatostatin receptor subtype II (SSTR) that can be non-invasively assessed by positron emission tomography (PET). Assessment of tumor heterogeneity is increasingly used as a tool for prognostication prediction. We investigated the potential of SSTR-PET to assess intraindividual tumor heterogeneity and thereby treatment response prior to PRRT.

METHODS

12 patients with progressive radioiodine-refractory differentiated (1 papillary, 1 oxyphilic, 2 oncocytic, 4 follicular) or medullary (n=4) TC were enrolled. SSTR-PET was performed at baseline. Conventional PET parameters and heterogeneity parameters were analyzed regarding their potential to predict progression-free (PFS, mean, 221 days) and overall survival (OS, mean, 450 days). Parameters of a subgroup of lesions (n=23) were also correlated with morphological response according to modified RECIST criteria.

RESULTS

In patient-based analysis, all conventional parameters failed to predict PFS. Several textural parameters showed a significant capability to assess PFS. Thereby, "Grey level non uniformity" had the highest area under the curve (AUC, 0.93) in Receiver operating characteristics analysis followed by "Contrast" (AUC, 0.89). In lesion-based analysis, only "Entropy" revealed potential to evaluate disease progression. OS could not be assessed by any parameter investigated.

CONCLUSIONS

Tumor heterogeneity seems to be a predictor of response to PRRT in patients with iodine-refractory differentiated/advanced medullary thyroid cancer and outperforms conventional PET parameters like standardized uptake value. In a "theranostic" approach, assessment of textural parameters may help in selecting patients who might benefit from PRRT.

Twenty-five years after Chernobyl: outcome of radioiodine treatment in children and adolescents with very high-risk radiation-induced differentiated thyroid carcinoma

CONTEXT

After severe reactor emergencies with release of radioactive iodine, elevated thyroid cancer risk in children and adolescents is considered the main health consequence for the population exposed.

DESIGN

We studied thyroid cancer outcome after 11.3 years' median follow-up in a selected, very high-risk cohort, 234 Chernobyl-exposed Belarusian children and adolescents undergoing postsurgical radioiodine therapy (RIT) in Germany.

INTERVENTIONS

Cumulatively 100 children with or (without; n = 134) distant metastasis received a median 4 (2) RITs and 16.9 (6.6) GBq, corresponding to 368 (141) MBq/kg iodine-131.

MAIN OUTCOME MEASURES

Outcomes were response to therapy and disease status, mortality, and treatment toxicity.

RESULTS

Of 229 patients evaluable for outcome, 147 (64.2%) attained complete remission [negative iodine-131 whole-body scan and TSH-stimulated serum thyroglobulin (Tg) < 1 μg /L], 69 (30.1%) showed nearly complete remission (complete response, except stimulated Tg 1-10 μg/L), and 11 (4.8%) had partial remission (Tg > 10 μg/L, decrease from baseline in radioiodine uptake intensity in ≥ 1 focus, in tumor volume or in Tg). Except for 2 recurrences (0.9%) after partial remission, no recurrences, progression, or disease-specific mortality were noted. One patient died of lung fibrosis 17.5 years after therapy, 2 of apparently thyroid cancer-unrelated causes. The only RIT side effect observed was pulmonary fibrosis in 5 of 69 patients (7.2%) with disseminated lung metastases undergoing intensive pulmonary surveillance.

CONCLUSIONS

Experience of a large, very high-risk pediatric cohort with radiation-induced differentiated thyroid carcinoma suggests that even when such disease is advanced and initially suboptimally treated, response to subsequent RIT and final outcomes are mostly favorable.

Frequency of transferrin receptor positive reticulocytes (TF-Ret) in blood as an indicator of total-body radiation exposure: a pilot study in nuclear medicine patients

Approximately 3-20% of all reticulocytes in blood of healthy persons are immature and transferrin receptor positive (Tf-Ret). Tf-Ret were measured by flow cytometry in 27 patients treated with three different radiopharmaceuticals labeled with (131)I and in 25 healthy controls. Patients were chronically exposed within 6 days to blood doses from 0.18-1.89 Gy (D6). Typically, two-thirds of D6 was administered within the first day (D1). The study had to be confined to intra-subject investigations due to high biological variability of Tf-Ret counts. A significant radiation-induced decline was found in patients D1 doses that were ≥0.5 Gy. Tf-Ret frequency declined during the first 4 to 5 days of nuclear therapy to about 30-60% of its initial value, and increased in the following 3 days without reaching the initial value. At the time of nadir, the relative frequency of Tf-Ret was more depressed than that of reticulocytes and lymphocytes. The relative Tf-Ret frequency at nadir could be fitted to the equation: %-Tf-Ret=exp-(D1/D(o)). D(o) was found to be 1.0 ± 0.4 Gy (Mean ± SEM). The study shows that Tf-Ret frequency in blood might be a good parameter for estimation of the radiation dose to red marrow.

Recombinant human thyrotropin to help confirm lack of evidence of radiation-induced differentiated thyroid cancer in young women seeking pregnancy

BACKGROUND

Women with a history of differentiated thyroid carcinoma who are contemplating pregnancy may wish reassurance regarding apparent remission. However, the thyroid hormone withdrawal needed to obtain serum thyroglobulin testing (Tg) results in weeks-long biochemical and clinical hypothyroidism, which could increase miscarriage and fetal death rates if pregnancy occurred during withdrawal of thyroxine or soon thereafter. Recombinant human thyrotropin (rhTSH) elevates thyrotropin exogenously, allowing uninterrupted thyroid hormone therapy and avoids hypothyroidism.

MATERIAL AND METHODS

Thirty female radiation-induced papillary thyroid carcinoma survivors who had undergone total- or near-total thyroidectomy and who were now seeking pregnancy (mean age 23.9 ± 1.8 years), and who were considered cancer-free by local standards, underwent rhTSH-aided Tg testing to help confirm remission. At the time of rhTSH testing, mean follow-up after primary surgical treatment was 11.1 ± 3.9 years, and all patients had negative neck ultrasonography, undetectable unstimulated serum Tg (< 0.2 ng/mL) and no interfering anti-Tg antibodies. However, based on T3, N1 or M1 status, 28/30 (93.3%) patients had high recurrence risk.

RESULTS

rhTSH produced no serum Tg increase in 27/30 women (90.0%). Serum Tg increases to 0.4-0.9 ng/ml were observed in 3 women, but careful neck ultrasonography found no lymphadenopathy. Reassured about their remission, 14/30 women (46%) have become pregnant and delivered healthy children in the 3 years since rhTSH-aided testing.

CONCLUSIONS

rhTSH-aided Tg testing is useful in confirming absence of tumor in female patients with a history of radiation-induced thyroid cancer who are seeking pregnancy, but who also have a high risk of thyroid cancer recurrence.

I-131 activities as high as safely administrable (AHASA) for the treatment of children and adolescents with advanced differentiated thyroid cancer

AIM

Differentiated thyroid carcinoma (DTC) in children and young adults is rare, can be aggressive, and often presents at advanced stages. In a population of young Belarusian patients with advanced DTC after the nuclear reactor accident at Chernobyl, we determined the activities that are as high as safely administrable (AHASA).

PATIENTS AND METHODS

In 180 children and adolescents, we studied 133 courses of I-131 thyroid remnant ablation (median age at ablation, 14.3 yr) and 250 courses of I-131 therapy (median age at therapy, 15.7 yr). Remnant ablation was performed with weight-adapted I-131 activities of a median of 51.8 MBq/kg (range, 23.9-73.8 MBq/kg); and residual disease therapy was performed with a median activity of 98.0 MBq/kg (range, 56.7-164.7 MBq/kg). The radiation absorbed dose to the blood (BD) per unit of activity administered for each treatment was deduced from whole-body retention data measured twice daily using ceiling probes. The AHASA activity was calculated assuming an upper limit of 2 Gy BD.

RESULTS

For I-131 ablation, the median weight-adjusted AHASA activity leading to a BD of 2 Gy was 407 MBq/kg (range, 137-661 MBq/kg). In three patients with extensive diffuse pulmonary metastases, the AHASA was lower than 200 MBq/kg. For patients receiving additional I-131 treatments after ablation, a median body weight-adapted AHASA activity of 406 MBq/kg (range, 210-775 MBq/kg) was calculated.

CONCLUSION

Children and adolescents with advanced DTC can be treated with I-131 activities of at least 200 MBq/kg. For children with extensive pulmonary metastases, pretherapeutic dosimetry is needed to determine the AHASA.

Success of the postoperative 131I therapy in young Belarusian patients with differentiated thyroid cancer after Chernobyl depends on the radiation absorbed dose to the blood and the thyroglobulin level

PURPOSE

Differentiated thyroid carcinoma (DTC) in children and young adults is rare but often aggressive and in an advanced stage at diagnosis. In a cohort of young Belarusian patients with advanced DTC after Chernobyl we retrospectively studied parameters influencing the success of the postoperative (131)I therapy.

METHODS

Included in the study were 136 patients (83 female, 53 male; median age 14.3 years, range 9.4-22.8 years) who had had total thyroidectomy in Belarus and subsequent (131)I therapy and follow-up in Germany. Of the 136 patients, 34 were classified as M1 and 102 as M0 (N0 1, N1 101). The median weight-adjusted (131)I activity administered after thyroid hormone withdrawal was 52 MBq/kg (range 24-74 MBq/kg). TNM stage, gender, administered activity, whole-body residence time and blood dose during ablation, Tg and TSH levels, date, and age at time of treatment were tested for their effect on the rate of complete remission (CR). CR was defined as a negative scan and a stimulated Tg level of <1 ng/ml at follow-up.

RESULTS

CR was observed in 1 of 34 M1 and in 51 of 102 M0 patients after the first treatment. Multivariate analysis in the M0 group identified the Tg level (P < 0.0001 for log(Tg)) and the radiation absorbed dose to the blood (P < 0.001) as independent determinants; all other parameters were unimportant (P > 0.3). The regression model was able to correctly predict CR in 82 of 102 patients (80.4%).

CONCLUSION

In children and young adults with advanced DTC, the rate of CR after postoperative (131)I therapy is dependent on the preablative Tg level and the radiation absorbed dose to the blood. Though the present results must be confirmed in a prospective study, they imply that preablative dosimetry may improve rates of CR.

The usual ultrasonographic features of thyroid cancer are less frequent in small tumors that develop after a long latent period after the Chernobyl radiation release accident

BACKGROUND

The Chernobyl accident resulted in an unprecedented number of radiation-induced thyroid cancers in young individuals as detected by national and international screening programs. The vast majority of thyroid malignancies were papillary carcinomas that, despite being similar by histopathology, displayed large variability in clinical course. The correlations between ultrasound (US) and clinicopathological features in young patients with radiation-induced thyroid cancer, however, have not been well studied. Because of the importance of US for deciding which subjects should have fine-needle aspiration biopsy, we assessed the US features of papillary thyroid carcinoma in patients exposed to Chernobyl fallouts.

DESIGN

We performed a retrospective multivariate logistic regression analysis of US features, clinicopathological data, and the latency period between radiation exposure and the diagnosis of cancer in 94 patients who were 10.6-34.3 years old (16.5 +/- 6.2, mean +/- standard deviation) at the time of diagnosis and 0.1-18.0 years old (5.6 +/- 4.2) at the time of the Chernobyl accident.

RESULTS

Nodules greater than 10 mm were associated with the higher frequency of irregular margins (p = 0.001), longer period of latency (p = 0.016), and bilateral lymph node involvement (p = 0.025). Irregular tumor margins correlated with the shorter period of latency (p = 0.009) and unilateral nodal disease (p = 0.010). Hypoechoic nodules were observed more frequently in female patients (p = 0.012), in the absence of halo (p = 0.003) or calcifications (p = 0.005). Hypoechogenicity also correlated with the shorter latency (p = 0.015) and younger age of patients (p = 0.048).

CONCLUSIONS

Irregular nodule margins, a usual sign of malignancy, are less useful in detecting thyroid cancers in radiation-exposed patients with tumors less than 10 mm. Thyroid cancers that are detected after longer latent periods display less of the US features characteristic of a malignant process, while benign US features are observed more frequently. Therefore, we recommend fine-needle aspiration biopsy to ensure early diagnosis of thyroid cancer for patients with a history of radiation exposure, even if their nodules are less than 10 mm.

Thyroid cancer in infants and adolescents after Chernobyl

Studies in children medically exposed to external irradiation more than 50 years ago revealed a considerably increased risk for thyroid cancer. Similarly, a strongly age-dependent risk for thyroid cancer was observed in the Japanese population after the atomic bomb explosions with the highest risk in the group of children below age of 10. After the Chernobyl accident, children from Belarus living in highly exposed regions received mean thyroid doses by radioactive fallout higher by a factor of approximately 2 as compared to the survivors of the atomic bomb explosions. This lead to a radiation related increase of thyroid cancer incidence in children and adolescents with the highest incidence in age group 0-4 years up to now totally amounting to approximately 5 000 cases. For screening of thyroid cancer in children, high resolution ultrasound is the method of choice which has to be complemented by fine-needle aspiration biopsy in suspicious cases. Diagnostic criteria for malignancy in childhood thyroid cancer by ultrasound are hypoechogenicity and irregularity of the outline, subcapsular location of lesions and increased peri-intranodular vascularisation. The treatment strategy for thyroid cancer in children does not differ substantially from the approach used in adults. Primary treatment consists of thyroidectomy and lymph node dissection. Careful and complete removal of the lymph nodes is of great clinical relevance in children because of very frequent node involvement (between 40% and 90%). Because of the high prevalence of lymph node metastases, ablation of thyroid remnants is mostly indicated in children with thyroid cancer. Distant metastases which need higher activities of radioiodine are less frequent with 10-20%. Even in advanced cases of childhood thyroid cancer, long-lasting remissions can be achieved. A specific finding in children is disseminated, milliary lung metastases with intense radioiodine uptake. In this situation, pulmonary fibrosis may be a severe side-effect so that the indication for repeated courses of radioiodine therapy has to be decided thoroughly. With respect to side-effects of radioiodine therapy, the risk of developing breast cancer has to be taken into account seriously since especially the female breast is exposed to a relatively high radiation dose. Generally, young patients treated with high activities of radioiodine should be carefully followed up during their whole lifespan.

Comprehensive clinical assessment of 740 cases of surgically treated thyroid cancer in children of Belarus

OBJECTIVE

A retrospective study was designed to evaluate the results of surgical treatment and follow-up data in thyroid cancer patients less than 15 years old at the time of surgery.

SUMMARY BACKGROUND DATA

Pediatric thyroid carcinomas have a high rate of lymph nodal and distant metastases. Risk factors for recurrences and postoperative morbidity have not been assessed yet in a representative series.

METHODS

The group included 740 pediatric patients with thyroid cancer. Total thyroidectomy was performed in 426 (57.6%), lobectomy in 248 (33.5%), subtotal thyroidectomy in 58 (7.8%) cases, and 8 patients (1.1%) underwent partial lobectomy.

RESULTS

The mean follow-up period was 115.8 months (range, 1.5-236.4 months). Recurrence was diagnosed in 204 cases (27.6%), including 73 local relapses (9.9%), 90 distant metastases (12.2%), and a combination of local and distant recurrences in 41 (5.5%) patients. Multivariate statistical assessment revealed the following independent parameters significantly associated with the risk of recurrent nodal disease: a young age at diagnosis, multifocal carcinomas, N1 status, and lack of neck lymph node dissection. For lung metastases, the significant risk factors were female gender, young age at diagnosis, and presence of symptoms. The observed 5- and 10-year survival for the entire group was 99.5% and 98.8%, respectively. Postoperative hypoparathyroidism was significantly associated with multifocal tumors, central compartment removal, and ipsilateral dissection.

CONCLUSIONS

Total thyroidectomy followed by radioiodine therapy is an optimal treatment strategy that makes it possible to achieve a cure in a vast majority of pediatric patients with differentiated thyroid carcinomas. Risk of recurrence is strongly associated with tumor stage, extent of surgery, the young patient's age, and presence of symptoms at diagnosis.

Evaluation of the reticulocyte micronucleus assay in patients treated with radioiodine for thyroid cancer

In the case of accidental radiation exposure, biological dosimetry has an important role. Previous studies have indicated that the flow cytometric micronucleus (MN) assay in human transferrin receptor positive reticulocytes (Tf-Ret) in blood could be a sensitive biomarker for chromosome damage. In the present investigation, the utility and sensitivity of this method was studied in 44 young patients from Belarus, who were treated with 131I for thyroid cancer. Red marrow (RM) is the critical organ in radioiodine therapy (RIT). In our patients, it was exposed to 100-700 mSv low-dose rate irradiation within 2-4 days. About 3 days after 131I administration, the frequency of micronucleated-Tf-Ret (f(MN-Tf-Ret)) increases within 1 day to a maximum and declines in the following 2-5 days to its value before treatment. A total dose of 100 mSv was easily detectable. The sensitivity of the assay after acute irradiation may be 50 mSv. The method should be useful for monitoring individuals after a radiation accident, provided blood samples can be obtained within a few days after exposure. The time-course of f(MN-Tf-Ret) is interpreted using a model, which considers the exponential exposure of red marrow in RIT as well as the kinetics of erythroblast maturation and reticulocyte migration into the peripheral circulation. Similar modelling was done on published data of MN in immature mouse erythrocytes. Striking similarities in the kinetic and in the yield of MN-induction were found between these two species. This lends support for the use of the mouse as a model for the MN-induction in humans.

The route of administration (oral vs intravenous) does not influence dose or outcome in Graves’ disease and unifocal autonomy

PURPOSE

In a prospective randomised study, we investigated the influence of the route of administration of radioiodide on dosimetry and therapy outcome.

METHODS

Fifty-four patients suffering from Graves' disease (GD) and 60 patients with unifocal autonomy (UA) participated in the study and were randomly treated with either orally or intravenously administered radioiodide. Pretherapeutic dosimetry was based on single uptake measurements with a calibrated uptake probe system. The radioiodine kinetics during hospitalisation was assessed by daily bedside uptake measurements. Therapeutic dose was determined by half-life and thyroid uptake at the time of discharge using the same uptake probe as for the radioiodine test.

RESULTS

No improvement in accuracy of dosimetry was achieved when radioiodide was administered intravenously. Mean therapeutic doses were identical following intravenous or oral administration. Variation in the achieved dose was slightly higher in the patients receiving oral administration, this being attributable to larger deviations in discrete activities of the capsules administered as compared with the values determined by dosimetry. No differences according to treatment modality were found with regard to therapeutic outcome. Eighty-seven patients attended 6-month follow-up after therapy. In the UA group, successful treatment, defined as a normal or elevated TSH level, was observed in 94% of patients after oral administration and in 80% after intravenous administration; corresponding figures in the GD group were 68% and 65%.

CONCLUSION

The causes of individual differences between targeted and therapeutically achieved doses remain undetermined. Variations in the bioavailability of radioiodide or other parameters affecting thyroid status may be involved, and further investigations are needed to clarify this.

Impact of Parathyroid Status and Ca and Vitamin-D Supplementation on Bone Mass and Muscle-Bone Relationships in 208 Belarussian Children after Thyroidectomy because of Thyroid Carcinoma

This observational study analyzes Ca-P metabolism and its impact on bone mass accrual and density and the muscle-bone mass/mass relationships in male and female children and adolescents who were parathyroidectomized because of thyroid carcinoma. Two hundred and eight children and adolescents (119 girls and 89 boys) from Gomel city (Belarus) and its rural surroundings were referred to our institution after having undergone total thyroidectomy for the treatment of advanced papillary thyroid cancer. A subgroup of children with demonstrated primary hypoparathyroidism received dihydrotachysterol (AT-10) and/or Ca supplementation. Among routine procedures over a maximum follow-up period of 5 years (average 3.7 years, maximum 8 visits), whole-body scans were taken using dual energy X-ray absorptiometry (DXA) at each visit in order to determine whole-body bone mineral content (TBMC), projected "areal" bone mineral density (TBMD), total lean mass (TLM) and total fat mass (TFM). The average serum Ca, P and AP concentrations over the whole observation period were significantly different between the groups; however, TBMC z-scores for all studied children were statistically similar in all visits. In girls, no between-group differences in height- and weight-controlled TBMC and TBMD or the TBMC/TLM ratio were observed (ANCOVA) and supplementation exerted no effect on these data, suggesting that the total bone mass accrual was not impaired by PTH deficiency in the studied conditions. However, non-supplemented boys showed lower values of the TBMC/TLM ratio than girls, and supplementation normalized these values in direct correlation with the induced improvement in serum P availability to bone. Results indicate that the primary impairment in parathyroid function and bone metabolism indicators in the thyroidectomized children was unrelated to any measurable change in crude bone mass values. However, in boys this condition impaired the TBMC/TLM ratio in such a way that the administered supplementation could normalize it as a function of improved P availability. Girls' skeleton seemed to have been naturally protected against the negative metabolic effect of the studied condition. An estrogen-induced enhancement of the biomechanical impact of muscle contractions on bone mass and structure could not be excluded in this group.

Micronucleus formation in lymphocytes of children from the vicinity of Chernobyl after (131)I therapy

After the Chernobyl accident a statistically significant increase in the number of children with thyroid tumours was observed. In this study 166 children with and 75 without thyroid tumours were analysed for micronucleus formation in peripheral blood lymphocytes using the cytochalasin B approach. The following factors did not significantly affect micronucleus formation: gender, age at the time of the first (131)I treatment, tumour stage, tumour type, or metastases; a statistically significant increase in the number of micronuclei, however, was observed for the residents of Gomel compared to other locations, such as Brest, Grodno, and Minsk. The children with tumours received (131)I treatment after surgical resection of the tumours. This gave us the opportunity to systematically follow the effect of (131)I on micronucleus formation. A marked increase was observed 5 days after the (131)I treatment followed by a decrease within a 4-7 months interval up to the next application, but the pre-treatment levels were not achieved. Up to 10 therapy cycles were followed each including an analysis of micronucleus formation before and 5 days after (131)I application. The response of the children was characterised by clear individual differences and the increase/decrease pattern of micronucleus frequencies induced by iodine-131 was correlated with a decrease/increase pattern in the number of lymphocytes.

Dose response for T-cell receptor (TCR) mutants in patients repeatedly treated with 131I for thyroid cancer

The T-cell receptor mutant frequency (TCR-Mf) was measured in 53 young adults, who were treated with radioiodine for thyroid cancer. Patients came from the southern part of Belarus. This region had suffered the most from the Chernobyl Disaster. TCR-Mf was determined by flow cytometry before and after 1 to maximal 10 treatments. Before treatment, TCR-Mf of patients was 2.0 x 10(-14). This Mf value is in the same range as that of young healthy students. After radioiodine therapy (RIT), TCR-Mf increases within about half a year to a maximum. The increase per one mGy to red marrow was 8.7 x 10(-7). After the maximum TCR-Mf declines exponentially. The half-life of TCR mutants was found to be 3.2 years. On the basis of these data, a calibration curve for the use of TCR-Mf as a biological dosimeter is given.

Inverse association between age at the time of radiation exposure and extent of disease in cases of radiation-induced childhood thyroid carcinoma in Belarus

BACKGROUND

Increased incidence of childhood thyroid carcinoma, particularly in the youngest children, has been reported from Belarus since the nuclear reactor accident at Chernobyl in 1986. The relation between disease severity and age at the time of the accident, not previously established in this cohort, was analyzed in this study.

METHODS

The authors studied the association between disease severity, expressed by TNM classification, and age at radiation exposure in a cohort of 483 patients younger than 8 years at the time of the Chernobyl accident who have been diagnosed with differentiated thyroid carcinoma since 1986 at the Center for Thyroid Cancer in Minsk. The associations between age at radiation exposure and TNM categories were compared among 4 groups of patients who were ages <2, 2.1-4, 4.1-6, and 6.1-8 years at the time of the accident. Multivariate discriminant analysis was performed to examine the effects of age at the time of the accident, gender, histology, tumor stage, and N classification on the frequency of distant metastasis.

RESULTS

Younger age at the time of the Chernobyl accident was associated with greater extrathyroidal tumor extension (P<0.01) and more lymph node involvement (P<0.0001) and tended to be associated with more distant metastases (P = 0.09). Compared with patients who were ages 6.1-8 years at the time of the accident, patients who were younger than 2 years had significantly more extrathyroidal tumor invasion (P = 0.004), lymph node involvement (P = 0.004), and distant metastases (P = 0.05). The age at diagnosis increased with older age at the time of radiation exposure (linear regression analysis; correlation coefficient = 0. 67; P<0.001). Multivariate analysis revealed that younger age at the time of the accident (P = 0.001) and advanced locoregional tumor extension (P<0.001) were the only powerful factors influencing the risk for distant metastasis of this malignancy.

CONCLUSIONS

The severity of disease was associated inversely with age at the time of radiation exposure in these cases of radiation-induced childhood thyroid carcinoma.

Comparison of total and regional body composition in adolescent patients with anorexia nervosa and pair-matched controls

Body composition in 31 adolescent girls suffering from anorexia nervosa (AN) was measured at the time of hospitalization in order to assess the muscle/bone relationship as a potential source of the development of osteopenia. Differences in lean tissue, fat and bone mass in total body, weight bearing and non weight bearing limbs were estimated in AN and pair-matched controls aged 14.2 +/- 1.8 years (range: 9-17 years). Further, it was investigated if bone mineral density (BMD) better reflects the muscle/bone relationship than bone mineral content (BMC). At the distal radius parameters measured by peripheral quantitative computed tomography (pQCT) were used to estimate the association of volumetric bone density to bone strength and lean body mass. The correspondence to the same and different body regions was assessed. Total lean mass in the controls was closely related to total body bone mineral content (TBBMC), as was lean tissue and bone mass of the limb subregions (r = 0.82 to 0.93). In contrast, the correlation was significantly lower in AN (r = 0.33 to 0.77). In the controls, the pQCT-derived bone strength was correlated with muscle mass of the forearm (r = 0.78, p < 0.001), but only moderately in AN (r = 0.47, n.s.). Regional lean tissue was 11-20% and fat mass was 56-66% lower in AN (p < 0.01). After adjustment for height, TBBMC was different at p = 0.01. Within the limbs subregions, BMC (but not BMD) was different in both groups only in the upper arm and the thigh. BMC reflected the bone/muscle relationship better than BMD. Intra- and between group regressions gave no significant differences between weight bearing and non weight bearing limbs. In conclusion, the assessment of musculoskeletal factors may be a useful tool to develop individual preventive measures for therapy after recovery of our patients.

Polymorphisms in the p53 gene in thyroid tumours and blood samples of children from areas in Belarus

We present changes in the p53 gene in a group of 70 thyroid tumours and 40 blood samples obtained from children from Belarus. Three thyroid tumours show a polymorphism in exon 6 (codon 213) and 5 tumours show a polymorphism in intron 6, 37 bp upstream to the 5'-end of exon 7. Only one patient has a mutation in exon 7 (codon 258) resulting in an amino acid substitution in the protein p53. The distribution of polymorphisms in the 40 blood samples was as follows: three patients had a polymorphism in exon 6 and two persons had a polymorphism in intron 6. One polymorphism in intron 6 was also found in the group of 30 healthy children from Belarus. The fact that the differences in the sequence in p53 found in the tumours was also seen in the blood of these patients demonstrates that they are polymorphisms not induced by radiation exposure. It is difficult to conclude, if the polymorphisms found by us could be associated with the predisposition to radiation-induced cancer.

Effect of specific activity on cardiac uptake of iodine-123-MIBG

Radioiodinated meta-iodobenzylguanidine (MIBG), an analog of norepinephrine, has been used to assess myocardial sympathetic innervation. Recent in vivo studies predict enhanced cardiac uptake of this radiopharmaceutical with high specific activity.

METHODS

To clarify the effect of specific activity on cardiac uptake of radioiodinated MIBG, the distribution and kinetics of no-carrier-added [123I]MIBG (> or = 7.4 TBq/mumol) were compared with those of commercial [123I]MIBG (approximately 74 MBq/mumol) in three healthy volunteers by serial imaging and blood sampling.

RESULTS

Higher specific activity result in higher uptake of radioiodinated MIBG in all volunteers in the heart (p < 0.05) and liver (p < 0.05) but not in the lung (p = 0.26). Due to rapid deiodination, a more pronounced accumulation of radioactivity was present in plasma after no-carrier-added MIBG than commercial [123I]MIBG, resulting in higher background and thyroid activity after administration of the former. Calculated heart-to-liver (p = 0.96) and heart-to-lung (p = 0.42) count ratios in all volunteers revealed no significant improvement in cardiac imaging with no-carrier-added [123I]MIBG compared to commercial [123I]MIBG.

CONCLUSION

This study highlights the appreciably higher in vivo deiodination of no-carrier-added [123I]MIBG compared to commercial preparation of [123I]MIBG in humans. Cardiac images acquired with no-carrier-added [123I]MIBG do not seem to be superior to those obtained with commercial MIBG.

Micronuclei in lymphocytes of children from the vicinity of Chernobyl before and after 131I therapy for thyroid cancer

The present study addresses the monitoring of children from the Belorussian and Ukrainian Republics exposed to the fall-out of the Chernobyl accident. Micronucleus analysis has been performed on 56 children from different areas. The micronucleus frequencies in individuals as well as in regional groups were comparable with controls, except for three donors. Such results had to be expected, taking into account that at least 7 years have passed since the accident. Most of the children whose micronucleus frequencies were determined are suffering from thyroid cancer and were treated by radioiodine (131I) therapy. We studied the effect of in vitro exposure with 131I on micronucleus induction and that proliferative ability of lymphocytes. The present investigation indicates that micronuclei can be usefully employed to detect individual exposures to the incorporated radionuclide within several days after the intake of the radionuclide in a dose range of around 65-390 mGy (effective dose).