Measuring the extent of total thyroidectomy for differentiated thyroid carcinoma using radioactive iodine imaging: relationship with serum thyroglobulin and clinical outcomes.
IMPORTANCE Despite performing total thyroidectomy (TT), postoperative radioactive iodine (RAI) imaging often demonstrates the presence of residual thyroid tissue within the operative bed. OBJECTIVE To measure the extent of TT using postoperative RAI imaging and assessing serum thyroglobulin (Tg) level for patients with differentiated thyroid carcinoma (DTC). DESIGN, SETTING, AND PARTICIPANTS We evaluated 245 patients undergoing TT for clinically staged cT1-3N0M0 DTC, who underwent diagnostic postoperative RAI imaging. INTERVENTIONS Total thyroidectomy. MAIN OUTCOMES AND MEASURES On the basis of quantitative measurements, RAI uptake (RAIU) in the thyroid bed of 0.2% of administered activity was selected as the cutpoint to determine the presence or absence of thyroid remnant. RESULTS By postoperative RAI imaging, TT in 106 patients (43%) resulted in RAIU of less than 0.2%. In the remaining 139 patients (57%), there was measurable iodine-avid thyroid tissue and/or tumor in the thyroid bed (n = 117 [84%]), the neck (n = 4 [3%]), or both (n = 18 [13%]). For the entire study population, mean 24-hour RAIU was 0.62%. Stimulated serum Tg levels were obtained in 232 of 245 patients (95%). Measurable stimulated Tg level (≥1 ng/mL) (to convert to micrograms per liter, multiply by 1) was found in 26 of 102 patients (25%) without thyroid remnant and in 87of 133 patients (65%) with thyroid remnant (P &lt; .001). CONCLUSIONS AND RELEVANCE A goal of postthyroidectomy RAIU of less than 0.2% helps maximize the likelihood of an unmeasurable postoperative Tg level, potentially simplifying follow-up evaluation and reducing the use of postoperative RAI in order to facilitate surveillance.
Department of Head & Neck Surgery, University of Texas MD Anderson Cancer Center, Houston6now with the Division of Head and Neck Surgery, Department of Otolaryngology, Stanford University School of Medicine, Stanford, California.
F Christopher
FC
Holsinger
Department of Head & Neck Surgery, University of Texas MD Anderson Cancer Center, Houston.
Uma
U
Ramaswamy
Department of Endocrine Neoplasia & Hormonal Disorders, University of Texas MD Anderson Cancer Center, Houston.
Maria E
ME
Cabanillas
Department of Head & Neck Surgery, University of Texas MD Anderson Cancer Center, Houston.
Juntian
J
Lang
Division of Quantitative Sciences, Department of Biostatistics, University of Texas MD Anderson Cancer Center, Houston.
Heather Y
HY
Lin
Department of Endocrine Neoplasia & Hormonal Disorders, University of Texas MD Anderson Cancer Center, Houston.
Naifa L
NL
Busaidy
Department of Surgical Oncology, University of Texas MD Anderson Cancer Center, Houston.
Elizabeth
E
Grubbs
Department of Nuclear Medicine, University of Texas MD Anderson Cancer Center, Houston.
Sania
S
Rahim
Department of Head & Neck Surgery, University of Texas MD Anderson Cancer Center, Houston.
Erich M
EM
Sturgis
Department of Surgical Oncology, University of Texas MD Anderson Cancer Center, Houston.
Jeffrey E
JE
Lee
Department of Head & Neck Surgery, University of Texas MD Anderson Cancer Center, Houston.
Randal S
RS
Weber
Department of Head & Neck Surgery, University of Texas MD Anderson Cancer Center, Houston.
Gary L
GL
Clayman
Department of Nuclear Medicine, University of Texas MD Anderson Cancer Center, Houston.
Eric M
EM
Rohren
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods*; D011184:Postoperative Period; D057234:Preoperative Period; D011877:Radionuclide Imaging; D015203:Reproducibility of Results; D013954:Thyroglobulin / Q000097:blood*; D013964:Thyroid Neoplasms / Q000097:blood / Q000000981:diagnostic imaging* / Q000601:surgery; D013965:Thyroidectomy; D016896:Treatment Outcome; D055815:Young Adult
D014408:Biomarkers, Tumor; D007457:Iodine Radioisotopes; D013954:Thyroglobulin