Nuclear medicine approaches in the monitoring of thyroid cancer patients.
OBJECTIVE
To evaluate the role of some nuclear medicine approaches such as (99m)Tc-MIBI scan and (131)I whole-body scintigraphy (WBS) in the monitoring of patients with differentiated thyroid cancer (DTC).


METHODS
95 patients (69F/26M) aged 17-74 years (mean 44.2) with DTC (56 cases with papillary, 20 with follicular and 19 with papillary-follicular carcinoma) were assessed. All of them had undergone total or near-total thyroidectomy and received radioiodine treatment for ablation of post-surgical residual thyroid tissue. They were examined after 4 weeks of L-thyroxin withdrawal in the follow-up of DTC. Planar and whole-body images were acquired at 15 and 180 min after i.v. administration of (99m)Tc-MIBI (555-740 MBq) and at 48 h after p.o. administration of(131)I(111-185 MBq) on Toshiba GCA gamma camera. Serum thyroglobulin (Tg) estimations were performed to clarify the presence of residual normal tissue or recurrent malignancy.


RESULTS
(131)I scan was positive in 63 patients showing thyroid remnants in 31 cases, lymph node metastases in 24 cases (17 to the neck, 7 to the neck/mediastinum), pulmonary metastases in 6 cases, bone and brain lesions in 2 cases. In 15 patients (131)I scan was negative, Tg was undetectable, so patients were considered tumor-free. In 17 patients (131)I scan was negative while serum Tg was increased. These false negative results were observed predominantly in cases with less differentiated metastatic disease, especially after several courses of high-dose (131)I therapy. (99m)Tc-MIBI scan revealed the presence of lymph node and/or lung metastases (non-functioning metastases) in 14 of them, false negative results were obtained in 2 cases, and one false positive in 1 case. Serum Tg was increased in all patients with local lymph node and distant metastases, visualized by (131)I or by (99m)Tc-MIBI, but also in 18 patients with thyroid remnants only.


CONCLUSIONS
(99m)Tc-MIBI scan has been reported to be a highly sensitive technique for the detection of DTC metastases that have lost the capability to uptake (131)I; the combined (99m)Tc-MIBI scintigraphy and serum Tg estimation appear to be an alternative method of radioiodine imaging in cases with DTC and elevated Tg.
Sergieva
S
S
Department of Nuclear Medicine, Sofia Cancer Centre, Bulgaria. sergieva_s@yahoo.com
Hadjieva
T
T
Doldurova
M
M
Stefanova
S
S
Dudov
A
A
D018263:Adenocarcinoma, Follicular / Q000000981:diagnostic imaging / Q000628:therapy; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging / Q000628:therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008207:Lymphatic Metastasis / Q000175:diagnosis; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000000981:diagnostic imaging; D010347:Patient Care Planning; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D017256:Technetium Tc 99m Sestamibi; D013954:Thyroglobulin / Q000097:blood; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000628:therapy; D013965:Thyroidectomy; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D013954:Thyroglobulin; D017256:Technetium Tc 99m Sestamibi