Impact of 131I SPECT/spiral CT on nodal staging of differentiated thyroid carcinoma at the first radioablation.
The purpose of this study was to determine the diagnostic value of 131I SPECT/spiral CT (SPECT/CT) on nodal staging of patients with thyroid carcinoma at the first ablative radioiodine therapy.


METHODS
Fifty-seven patients were studied using SPECT/CT 3-4 d after receiving 3.96+/-0.5 GBq of 131I for radioablation of thyroid remnants after a thyroidectomy for differentiated thyroid carcinoma. In addition to planar whole-body scintigraphy, SPECT/CT of the neck was performed using a hybrid camera combining a double-head SPECT camera with either a 2-slice (n=23) or a 6-slice (n=34) spiral CT scanner. The planar scans and the SPECT/CT images were evaluated for cervical tracer uptake independently of each other and of the clinical findings.


RESULTS
SPECT/CT led to a revision of the original diagnosis in 28 of 143 cervical foci of radioiodine uptake seen on planar imaging. In particular, SPECT/CT reclassified as benign 6 of 11 lesions considered to be lymph node metastases and 11 of 15 lesions considered to be indeterminate. Furthermore, SPECT/CT allowed the identification of 11 lymph node metastases classified as thyroid remnant or as indeterminate on planar imaging. Based on this revision, SPECT/CT yielded a gain in information on nodal stage in 20 of the 57 patients studied (35%, P<0.03). SPECT/CT altered nodal stage from N0 to N1 in 2 of 20 patients and from indeterminate (Nx) to N1 in 6 of 30 patients. The result was a change in risk stratification conforming to the classification proposed by the International Union Against Cancer in 14 patients (25%).


CONCLUSIONS
SPECT/CT determines lymph node involvement at radioablation performed for thyroid cancer more accurately than does planar imaging. SPECT/CT may alter management in roughly one quarter of patients with thyroid carcinoma by upstaging or downstaging their disease.
Schmidt
Daniela
D
Clinic of Nuclear Medicine, Institute of Radiology, University of Erlangen-Nürnberg, Erlangen, Germany. Daniela.Schmidt@uk-erlangen.de
Szikszai
Attila
A
Linke
Rainer
R
Bautz
Werner
W
Kuwert
Torsten
T
D055011:Ablation Techniques; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000378:metabolism; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D008207:Lymphatic Metastasis / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000601:surgery*; D015899:Tomography, Emission-Computed, Single-Photon; D036542:Tomography, Spiral Computed; D051598:Whole Body Imaging
D007457:Iodine Radioisotopes