title: [Diagnostic modalities in patients affected by differentiated thyroid carcinoma with high thyroglobulin levels and total body Iodium-131 negative: PET/CT use after recTSH].
abstract: In the follow-up of differentiated thyroid carcinoma (DTC), after total thyroidectomy and Iodine-131 therapy, thyroglobulin (Tg) levels and Iodine-131 total body have particular importance. The Tg level becomes a specific and very sensitive marker of DTC recurrence: it is usually evaluated after eradication of thyroid residual tissue (by thyroidectomy and radiometabolic therapy), in presence of high level of TSH (>35 microU/ml) obtained with the suspension of therapy or after rec-TSH administration and in absence of anti-Tg antibodies. Usually, to solve diagnostic problems in patients with negative total body Iodine-131 and high levels of thyroglobulin, we consider one or more of the following investigations, on the basis of prognostic factors: radiological examinations (neck US, skeletal X-ray, CT chest and abdomen, MRI) and scintigraphy (bone scintigraphy, Tc-MIBI or Tl-201 scintigraphy, octreoscan, PET/CT). The use of PET is well known in patients in whom carcinoma metastases are strongly suspected and who are unable of concentrating Iodine-131. In order to increase the PET sensitivity, scintigraphy is performed with high TSH levels obtained through a rec-TSH injection on the 1st and 2nd day, PET/CT scan and blood withdrawal (for Tg level evaluation) on the 3rd day. Considering the hypothesis of a recurrence with lesion size below the resolution power of the diagnostic equipment (5 mm), if PET/CT results are negative, the patients are strictly followed-up and Tg is monitored every 4-6 months. An alternative hypothesis might be not to consider the negative-PET patients as sick persons, but to attribute high Tg levels to illegitimate transcription of mRNA for Tg by the non-thyroid cells or to ectopic thyroid tissue (e.g. intrathymus). Positive PET/CT patients are evaluated for a possible surgical removal of the lesions or alternative appropriate therapies.
authors.affiliation: S. C. Medicina Nucleare, Ospedale Niguarda Cà Granda, Milan.
authors.forename: G
authors.initials: G
authors.lastname: Biscontini
authors.forename: M
authors.initials: M
authors.lastname: Possa
authors.forename: R
authors.initials: R
authors.lastname: Sara
authors.forename: M
authors.initials: M
authors.lastname: Milella
authors.forename: C
authors.initials: C
authors.lastname: Rossetti
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000097:blood* / Q000235:genetics; D002277:Carcinoma / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000628:therapy; D005189:False Positive Reactions; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008279:Magnetic Resonance Imaging; D015282:Octreotide / Q000627:therapeutic use; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D013954:Thyroglobulin / Q000097:blood* / Q000235:genetics; D013964:Thyroid Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000628:therapy; D013965:Thyroidectomy; D014057:Tomography, X-Ray Computed; D014158:Transcription, Genetic; D014463:Ultrasonography
chemical_list: D018931:Antineoplastic Agents, Hormonal; D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013954:Thyroglobulin; D017256:Technetium Tc 99m Sestamibi; D015282:Octreotide