A cutoff thyroglobulin value suggestive of distant metastases in differentiated thyroid cancer patients

Serum thyroglobulin is used as part of the early postoperative assessment of differentiated thyroid cancer (DTC) since there is a clear relationship between an increased risk of recurrence and persistent disease after initial treatment and high postoperative stimulated thyroglobulin (ps-Tg) values. Thus, although ps-Tg above 10-30 ng/mL is considered an independent predictor of worse prognosis, the value that is associated with distant metastases is not defined. Thus, this was our objective. We selected 655 DTC patients from a nuclear medicine department database (Irmandade Santa Casa de Misericórdia de São Paulo, Brazil). All patients had received total thyroidectomy and radioactive iodine (RAI) therapy and had ps-Tg values higher than 10 ng/mL with negative anti-thyroglobulin antibodies. Then, we selected patients who presented post-therapy whole-body scan with pulmonary and/or bone uptake but with no mediastinum or cervical uptake. Patients with negative findings on functional imaging or any doubt on lung/bone uptake were submitted to additional exams to exclude another non-thyroid tumor. Of the 655 patients, 14.3% had pulmonary and 4.4% bone metastases. There was a significant difference in ps-Tg levels between patients with and without metastases (P<0.001). The cutoff value of ps-Tg was 117.5 ng/mL (sensitivity: 70.2%; specificity: 71.7%) for those with lung metastasis, and 150.5 ng/mL (sensitivity: 79.3%; specificity: 85%) for those with bone metastasis. The cutoff value for patients with eitherpulmonary or bone metastasis was 117.5 ng/mL (sensitivity: 70.2%; specificity: 83.7%). Our findings demonstrated that ps-Tg could predict distant metastasis in DTC patients. We identified a cutoff of 117.5 ng/mL with a high negative predictive value of 93.7%.

Impact of nutritional iodine optimization on rates of thyroid hypoechogenicity and autoimmune thyroiditis: a cross-sectional, comparative study

BACKGROUND

Since several countries have established mandatory food iodine fortification, there has been a decrease in rates of iodine deficiency disorders in parallel with an increase in prevalence of autoimmune thyroid diseases. This study compared the nutritional iodine status and the prevalence of autoimmune thyroiditis and thyroid hypoechogenicity on ultrasound in schoolchildren in São Paulo (Brazil) in two distinct periods of time in which fortified salt had different concentrations of iodine.

METHODS

We conducted a cross-sectional study evaluating 206 children aged 7-14 years and without a history of thyroid disease. Assessments included measurements of thyrotropin (TSH), free thyroxine, antithyroperoxidase (anti-TPO), and antithyroglobulin (anti-TG) antibodies, urinary iodine concentration, and thyroid ultrasound.

RESULTS

Mean urinary iodine concentration was 165.1 μg/L. Eleven children (5.3%) were diagnosed with autoimmune thyroiditis based on at least two of four criteria adopted in our study: positive anti-TPO or anti-TG antibody, hypoechogenicity of the thyroid parenchyma on ultrasound, and a TSH >4.0 μU/mL. Comparing our results with those from a similar study conducted during a period in which concentrations of iodine in the salt were higher (median urinary iodine concentration >300 μg/L), we observed a trend toward a lower prevalence of autoimmune thyroiditis, although no definitive conclusion could be established.

CONCLUSION

The current nutritional iodine status in our cohort was within optimal levels and lower than levels found in 2003. The prevalence of autoimmune thyroiditis seems to be decreasing in parallel with a decrease in iodine intake, although we could not reach a definitive conclusion.

Correction factors for more accurate estimates of exposure rates near radioactive patients: experimental, point, and line source models

Radioactive patients may expose others after radiopharmaceutical administrations, and evaluation of the absorbed dose or exposure rates close to patients is important in keeping radiation doses as low as reasonably achievable. Two theoretical exposure models, point source and line source models, are frequently used to calculate exposure or dose rates without the support of actual measurements. If measurements of exposure rates were performed near patients, an experimental exposure model could be implemented. When measurements of exposure rates are performed, these measurements are made inside therapy rooms or other confined places, in which case scattered radiation may significantly influence the measurements. In this study we measured exposure rates from radioactive patients without the influence of scattered radiation and determined correction factors for the theoretical exposure models. The exposure rates from a total of 110 radioactive patients were measured at 1.0 h after oral administration of Na131I for thyroid therapy; the results +/-1 SD at distances of 0.5, 1.0, 1.5, 2.0, 3.0, and 4.0 m in front of the patients were (29 +/- 6), (9.9 +/- 1.7), (4.6 +/- 0.9), (2.7 +/- 0.5), (1.31 +/- 0.25) and (0.74 +/- 0.12) x 10(-10) C kg(-1) MBq(-1) h(-1) [1.0 x 10(-10) C kg(-1) MBq(-1) h(-1) = 14.34 x 10(-6) R mCi(-1) h(-1)], respectively. To obtain more accurate estimates of the actual exposure rates from patients using the theoretical exposure models, we found that correction factors should be applied; the functions CFEM = 1.19 + 32.80e(5.92D) and CFLS = 0.022LnD + 0.639 describe these correction factors for distances less than or equal to 1.0 m from the patients for experimental and line source exposure models, respectively. The function that describes the correction factors to the point source model is CFPS = 0.224LnD + 0.638 at the same distances; applying these correction factors leads to a reduction from 56% to 1% in the difference between measured exposure rates and theoretical exposure rates calculated by the point source exposure model at a distance of 1.0 m from patients. The results given here provide more accuracy in evaluation of exposure rates and consequently absorbed doses near radioactive patients and allow for more effective radiological protection procedures during patient management.

Tratamento do carcinoma diferenciado da tireóide com iodo-131: intervenções para aumentar a dose absorvida de radiação

OBJETIVO: Analisar medidas tomadas para aumentar a dose de radiação absorvida (DOSE) durante o tratamento do carcinoma diferenciado da tireóide (CDT) com iodo-131. MÉTODOS: As abordagens para aumentar a DOSE na radioiodoterapia são: redução da competição com iodo não-radioativo, estímulo da captação/retenção celular e aumento da atividade administrada. Revisaram-se os fundamentos e resultados de cada um destes métodos. RESULTADOS: Apesar de ser difícil confirmar aumento de sobrevida, existe relação direta entre a DOSE e a resposta no CDT. Diferentes abordagens permitem o aumento da DOSE nos tecidos, inferindo-se uma possível melhora na resposta dos tumores ao tratamento com iodo-131. Apesar do prognóstico relativamente benigno da doença, a melhoria da resposta é importante nos casos de alto risco, em que as alternativas de tratamento são limitadas. CONCLUSÕES: As intervenções descritas permitem aumentar a DOSE durante o tratamento do CDT, podendo ser empregadas para casos de alto risco.