Procedure:
This is a prospective study which included 20 patients who were under follow up at nuclear medicine and PET/CT unit in Nasser oncology center during the period from July 2017 to July 2019.
Patients met the following inclusion criteria:
- Histopathologically proved differentiated thyroid carcinoma.
- Total radio-surgical thyroid ablation.
- Elevated serum Thyroglobulin levels (> 10ng/ml in patients with stimulated TSH level and >1ng/ml in patients with suppressed TSH level).
- Negative I (131) whole body scan.
Exclusion criteria were as follow:
- Thyroglobulin level (<10ng/ml in patients with stimulated TSH level and <1ng/ml in patients with suppressed TSH.
- Positive I (131) whole body scan.
- Pathology other than DTC (e.g. undifferentiated or medullary thyroid carcinoma).
- Incomplete radio-surgical thyroid ablation.
Results:
- FDG PET/CT based analysis showed that 19 true positives and 1 was true negative as confirmed by the gold standard (Histopathology and clinical follow-up).
- 13 patients had either local recurrence or lymph node metastases without distant metastatic disease, 6 patients had different distant metastasis.
- FDG PET CT based analysis showed that 19 true positives and 1 was true negative as confirmed by the gold standard (Histopathology and clinical follow-up).
- The sensitivity & accuracy of PET &PET/CT The sensitivity & accuracy of PET/CT (95%) were significantly better than those of the CT alone (84.2% and 80%, respectively) [P=0.03].
Case Review:
Case 1
A 55 year old female patient, who underwent near-total thyroidectomy, followed by RAI-131 ablation for multi-centric papillary cancer thyroid. During follow up elevated thyroglobulin level = 15mg/dl was detected, I (131) whole body scanning and neck ultrasound were negative, PET/CT was done and revealed solitary small sized left lower lung lobe pulmonary nodule SUVmax~11.8 , which insures the diagnosis of metastatic nature of this lesion.
Fig. 1: Axial fused PET/CT image shows metabolically active pulmonary nodule.
Case 2
30 year old female patient, who underwent total thyroidectomy, followed by 120 mCi RAI-131 ablation for papillary cancer thyroid. During follow up elevated thyroglobulin level= 17mg/dl was detected, I (131) whole body scanning was negative; PET/CT was done and revealed metabolically active small right para-tracheal lymph node with max SUV~6.
Fig. 2: Axial fused image PET/CT shows right para tracheal lymph node.
Fig. 3: Axial fused image PET only shows right para tracheal lymph node.
Case 3
A 27 year old male patient, who underwent total thyroidectomy, followed by 120 mCi RAI-131 ablation for papillary cancer thyroid. Follow up I (131)whole body scanning done one year later and was negative in spite of elevated hyroglobulin level=12 mg/dl).PET/CT was done and revealed right retro-mandibular /preauricular soft tissue nodule likely nodal with SUVmax~7.2.
Fig. 4: axial PET only showed right retro-mandibular soft tissue nodule
Fig. 5: Coronal fused PET/CT image showed right retro-mandibular soft tissue nodule
Case 4
A 28 year old female patient underwent total thyroidectomy and RAI ablation for papillary cancer thyroid. Follow up revealed elevated thyroglobulin level=29 mg/dl with negative Iodine WBS and neck ultrasound. CT revealed small anterior mediastinal prevascular lymph node, PET/CT was done and revealed metabolically active small anterior mediastinal lymph node.
Fig. 6: Axial fused PET showed anterior mediastinlal lymph node.
Fig. 7: Axial fused PET/CT image shows anterior mediastinlal lymph node