Are posttherapy radioiodine scans informative and do they influence subsequent therapy of patients with differentiated thyroid cancer?
Posttherapy scans (PTS) with a gamma camera are typically used after therapeutic doses of 131I to visualize metastases that may not be seen with lower dose diagnostic scans. During a 16-month period, we studied 81 patients (64 with papillary thyroid cancer and 17 with follicular thyroid cancer), who had both a diagnostic whole-body scan (131I dose 3 mCi) and a PTS. A total of 117 PTS were evaluated. At the time of PTS, clinical or radiologic evidence of metastatic or residual disease was present in 68 patients (84%). The anatomic sites of known disease included, neck (63), mediastinum (23), lung (35), bone (14), trachea (16), esophagus (5), and brain (2). PTS showed focal areas of abnormal uptake not seen in diagnostic scans in 15 scans (13%). Areas with abnormal new uptake included: neck (5), lung (5), mediastinum (4), bone (2), and adrenal (1). In 7 patients (9%) the PTS results impacted future decisions regarding plans for subsequent diagnostic scanning and 131I therapy or changed the patient's risk group category.


CONCLUSIONS
(1) 13% of 117 PTS demonstrated abnormal foci of 131I uptake not seen on pretherapy scans and (2) PTS changed management strategy in 9% of the studied patients.
Fatourechi
V
V
Division of Endocrinology and Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA. fatourechi.vahab@mayo.edu
Hay
I D
ID
Mullan
B P
BP
Wiseman
G A
GA
Eghbali-Fatourechi
G Z
GZ
Thorson
L M
LM
Gorman
C A
CA
D018263:Adenocarcinoma, Follicular / Q000000981:diagnostic imaging / Q000532:radiotherapy; D000328:Adult; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging / Q000532:radiotherapy; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D008207:Lymphatic Metastasis; D008297:Male; D008479:Mediastinal Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D008875:Middle Aged; D009362:Neoplasm Metastasis / Q000000981:diagnostic imaging*; D011877:Radionuclide Imaging; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D014134:Tracheal Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary
D007457:Iodine Radioisotopes