Recombinant Thyrotropin PET-CT Fusion Scanning in Thyroid Cancer

Utility of Recombinant Human Thyrotropin (rTSH) PET-CT Fusion Scanning to Identify Residual Well-differentiated Epithelial Thyroid Cancer

The purpose of this study is to determine [for patients with previously treated well-differentiated thyroid cancer and evidence of residual disease based on serum thyroglobulin (Tg) level] whether positron emission tomography-computed tomography (PET-CT) fusion scanning performed after recombinant thyroid-stimulating hormone (TSH) (rTSH, thyrotropin alfa for injection) will be more sensitive for the detection of disease sites than PET-CT scanning without rTSH. The study will also determine if this information will significantly alter the therapeutic approach in some patients.

PET/CT was performed before (basal PET) and 24 - 48 h after rhTSH administration (rhTSH-PET) in 63 patients (52 papillary and 11 follicular thyroid cancers). Images were blindly analyzed by two readers. The proposed treatment plan was prospectively assessed before basal PET, after basal PET, and again after rhTSH-PET.

Inclusion Criteria:

• Adults (aged ≥ 18 years) with history of treated well-differentiated epithelial thyroid carcinoma (papillary, follicular or Hurthle cell), for which total or near total thyroidectomy plus postoperative radioiodine remnant ablation with 131-I has either been performed or found to be unnecessary by radioiodine imaging after TSH stimulation.
• Serum thyroglobulin (Tg) concentration ≥ 10 ng/mL (in the absence of interfering Tg autoantibodies).
• No findings of a "qualifying" radioiodine whole body scan that are sufficient to localize the disease suspected on the basis of the serum Tg.
• Inconclusive disease localization despite clinical assessment, cervical sonography, CT or magnetic resonance (MR) of the chest, and when appropriate other imaging and biopsy procedures. Patients must have no more than three foci of known or suspected extra-cervical metastasis.
• Must be in stable medical condition.
• Must be able to fully understand the protocol and be compliant with instructions.

Exclusion Criteria:

• Diabetes mellitus, due to interference with fluorodeoxyglucose (FDG) PET scanning.
• Claustrophobia, inability to lay supine, or other factors preventing cooperation with scanning procedures.
• Withdrawal of thyroid hormone or rTSH administration within the preceding month.
• Presence of circulating Tg autoantibodies interfering with serum Tg measurement.
• Women who are pregnant or breastfeeding