2009, Number 4
Valor de la gammagrafía con Tc-99m-tetrofosmín en el diagnóstico del cáncer bien diferenciado de tiroides
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ABSTRACTBackground: Patients with cold thyroid nodules without ultrasound malignant suspicion and with benign/undetermined cytology may be subjected to follow-up surveillance. 99mTCtetrofosmin scan (99mTC-TS) may identify patients where this observation can be performed with more certainty. Absence of uptake never occurs in carcinoma patients. Our objective was to determine the 99mTC-TS negative predictive value (NPV) in patients with cold thyroid nodules. Methods: An evaluation with 99mTC-TS was conducted prior to surgery in patients with thyroid gland tumor who were candidates for surgery. All patients underwent thyroidectomy according to histology; NPV and test sensitivity were evaluated when compared with the histopathological result. Then, 296-370 MBq (8-10 mCi) of 99mTC-tetrofosmin was administered; scan images were evaluated after 120 min. Scan result was reported as a) with increased metabolic activity (IMA) or b) without increased metabolic activity (WIMA). Results: Included in the study were 86 consecutive patients. In 60 patients, the scan showed IMA, 20/60 (33%) with carcinoma, 67% with benign nodule. In 26 (30.2%) the scan was WIMA, in this group 3/26 (11.5%) had carcinoma and (88.4%) had a benign neoplasia. Sensitivity = 91.43 (95% CI = 80.73-100), specificity = 45.10 (95% CI = 30.46-59.73), positive predictive value = 53.33 (95% CI = 39.8-66.79) and NPV = 88.46 (95% CI 74.26-100). Negative probability ratio = 0.19. Conclusions: IMA-99mTC-TS is less specific in thyroid cancer; nevertheless, in WIMA patients the possibility of carcinoma is 13%. Most patients (70%) showed IMA, 33% with carcinoma. WIMA-NPV = 30%. 99mTC-TS may be useful in therapeutic decision of patients with thyroid nodule with concerns about surgery. Its usefulness lies in the NPV.
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