PET con 18FDG en pacientes con cáncer diferenciado de tiroides que presentan niveles elevados de tiroglobulina sérica y rastreos con 131I negativos / F-18-Fluordeoxyglucose positron emission tomography on patients with diferentiated thyroid cancer who present elevated human serum thyroglobulin levels and negative I-131 whole body scan

RESUMEN

El objetivo de estudio fue valorar el papel de la tomografía por emisión de positrones con 18F-fluordeoxiglucosa (PET-FDG) en los pacientes con cáncer diferenciado de tiroides, niveles de tiroglobulina sérica (hTg) elevados y rastreo de cuerpo completo con radioyodo negativo (RCC). Material y métodos: Se estudiaron con PET-FDG 54 pacientes (37 mujeres y 17 hombres) con edades comprendidas entre los 17 y los 88 años, 45 con carcinomas papilares y 9 con foliculares de tiroides con sospecha de recurrencia/metástasis de su enfermedad por elevación de los niveles de hTg (hTg > 2 ngr/ml) en presencia de valores estimulantes de la TSH (≥ 30 μIU/ml) y en los que el RCC era negativo. Los RCC se realizaron con dosis diagnósticas (185 MBq). Las PET-FDG se efectuaron tras la administración i.v. en ayunas de 370 MBq de FDG hallándose el paciente bajo su tratamiento hormonal sustitutivo habitual. Previamente a la realización de la PET-FDG, 14 pacientes habían sido estudiados por gammagrafía con 99mTc-metoxi-isobutiril-isonitrilo (MIBI), mientras que a 26 se les había realizado tomografía computerizada (TC). Resultados: Un total de 25 de los 54 PET-FDG mostraron focos patológicos de captación del trazador (46,29 %). Se observó asociación significativa entre la positividad de la PET y los niveles de hTg mayores de 10 ng/ml en el momento de esta exploración (en tratamiento sustitutivo). La gammagrafía con 99mTc-MIBI era positiva en 7 de los 14 pacientes a los que se les realizó, y esta positividad fue congruente con la PET-FDG en 4/7. Todas las lesiones detectadas por la TC fueron visualizadas en la PET-FDG, mientras que 12 de los 21 pacientes con TC negativa tenían evidencia de recurrencia de la enfermedad detectada por la PET-FDG. Conclusiones: Nuestros resultados sugieren que la PET-FDG sería una técnica de gran utilidad en el seguimiento de los pacientes diagnosticados de carcinoma diferenciado de tiroides con niveles de hTg elevados y RCC negativos. Su utilidad sería superior si los valores de hTg fuesen mayores de 10 ng/ml

ABSTRACT

This study aimed to evaluate the role of Fluorine-18-fluorodeoxyglucose positron emission tomography (PET-FDG) in patients with elevated serum thyroglobulin (hTg) levels where thyroid cancer tissue does not concentrate radioiodine, rendering false-negative results on I-131 scanning. Material and methods: Whole-body PET imaging using FDG was performed in 54 patients (37 female, 17 male) aged 17-88 years 45 with papillary tumors and 9 with follicular tumors who were suspected of having recurrent thyroid carcinoma due to elevated thyroglobulin levels (hTg > 2 ng/ml) under thyroid-stimulating hormone (TSH ≥ 30 μIU/ml) in whom the iodine scan was negative. All whole body scans were obtained with diagnostic doses (185 MBq). Whole body PET imaging was performed in fasting patients following i.v. administration of 370 MBq FDG while the patients were receiving full thyroid hormone replacement. Before PET, 99mTc methoxyisobutylisonitrile scintigraphy (99mTc-MIBI) was done in 14 patients and morphologic imaging in 26 by CT scan. Results: Positive PET results confirmed the presence of hypermetabolic foci in 25/54 patients (46.29 %). Positive findings were found for PET-FDG in patients with hTg levels higher than 10 ng/ml receiving full thyroid hormone replacement. 99mTc-MIBI demonstrated lesions in 7/14 patients (50 %). PET-FDG and 99mTc-MIBI had congruent positive results in 4/7 patients. All the lesions found by CT were detected by PET-FDG, while recurrent disease was found in 12/21 patients with previous negative CT. Conclusions: These results suggest that PET-FDG seems to be a promising tool in the follow-up of thyroid cancer and should be considered in patients suffering from differentiated thyroid cancer with suspected recurrence and/or metastases by elevated thyroglobulin levels, and negative I-131 whole body scans. PET-FDG might be more useful at hTg levels > 10 ng/mlThis study aimed to evaluate the role of Fluorine-18-fluorodeoxyglucose positron emission tomography (PET-FDG) in patients with elevated serum thyroglobulin (hTg) levels where thyroid cancer tissue does not concentrate radioiodine, rendering false-negative results on I-131 scanning. Material and methods: Whole-body PET imaging using FDG was performed in 54 patients (37 female, 17 male) aged 17-88 years 45 with papillary tumors and 9 with follicular tumors who were suspected of having recurrent thyroid carcinoma due to elevated thyroglobulin levels (hTg > 2 ng/ml) under thyroid-stimulating hormone (TSH ≥ 30 μIU/ml) in whom the iodine scan was negative. All whole body scans were obtained with diagnostic doses (185 MBq). Whole body PET imaging was performed in fasting patients following i.v. administration of 370 MBq FDG while the patients were receiving full thyroid hormone replacement. Before PET, 99mTc methoxyisobutylisonitrile scintigraphy (99mTc-MIBI) was done in 14 patients and morphologic imaging in 26 by CT scan. Results: Positive PET results confirmed the presence of hypermetabolic foci in 25/54 patients (46.29 %). Positive findings were found for PET-FDG in patients with hTg levels higher than 10 ng/ml receiving full thyroid hormone replacement. 99mTc-MIBI demonstrated lesions in 7/14 patients (50 %). PET-FDG and 99mTc-MIBI had congruent positive results in 4/7 patients. All the lesions found by CT were detected by PET-FDG, while recurrent disease was found in 12/21 patients with previous negative CT. Conclusions: These results suggest that PET-FDG seems to be a promising tool in the follow-up of thyroid cancer and should be considered in patients suffering from differentiated thyroid cancer with suspected recurrence and/or metastases by elevated thyroglobulin levels, and negative I-131 whole body scans. PET-FDG might be more useful at hTg levels > 10 ng/ml