ABSTRACT
BACKGROUND: Differentiated thyroid cancer (DTC) work-up is based on (near)total-thyroidectomy plus thyroid remnant ablation (TRA) with 131-radioiodine in many patients, and long-life follow-up. 131I-post therapy whole body scan (pT-WBS) and serum thyroglobulin (Tg) are used in identifying metastatic patients. Some authors have evaluated the possibility of using post-surgical Tg (ps-Tg) values in deciding for or against TRA. The aim of our study was to verify the diagnostic accuracy of 131I-pT-WBS and SPECT/CT imaging (post-therapeutic imaging) compared to serum Tg levels in detecting metastases in early stage of DTC patients. RESULTS: Post-therapeutic imaging revealed metastases in 82 out of 570 (14.4%) patients. Metastases were successively confirmed by other diagnostic tools or by histology (sensitivity and PPV = 100%). Seventy-three out of 82 patients (90.2%) showed ps-Tg levels ≤1 ng/ml. In fifty-four per cent of patients, serum Tg levels at TRA remained ≤1 ng/ml. CONCLUSION: In conclusion, ps-Tg levels cannot be used in deciding for or against TRA. In early stage of DTC, post-therapeutic imaging (131I-pT-WBS and SPECT/CT) is an accurate method of detecting metastases, also in patients with stimulated serum Tg values ≤1 ng/ml. METHODS: We retrospectively reviewed the records of 570 consecutive patients affected by pT1-pT3 DTC (F = 450, M = 120), referred to our Nuclear Medicine Units in the last five years to perform TRA after (near)-total-thyroidectomy.All patients underwent TRA 3-4 months after thyroid surgery either in euthyroid or in hypothyroid state. Serum Tg values evaluated in post-surgical period and at TRA were matched with post-therapeutic imaging results.
ABSTRACT
BACKGROUND: Differentiated thyroid cancer (DTC) is the most common endocrine malignancy. In recent decades, the incidence has been increasing, largely due to increased detection of patients with low-risk or very low-risk DTC. According to European Thyroid Association and American Thyroid Association guidelines, radioiodine (RAI) thyroid remnant ablation is not indicated in very low-risk patients, while its role is still debated in low-risk patients. Accordingly, risk stratification of DTC patients is pivotal when deciding for or against RAI ablation. Presently, risk stratification is based on pTNM staging integrated with clinical parameters. The aim of our study was to evaluate the relationship between location of malignant thyroid nodules within the thyroid gland and the presence of loco-regional and/or distant metastases in patients with pT1a-pT1b DTCs. METHODS: We reviewed the records of 246 patients (214 women, 32 men; female-to-male ratio 6.7:1) affected by unifocal DTC ≤ 2 cm, who had undergone RAI thyroid remnant ablation (activity ranged 555-4588 MBq) after levothyroxine withdrawal or after recombinant human TSH (rhTSH) stimulation. The majority of the patients (91.5%) were affected by papillary thyroid carcinoma. RESULTS: Metastases were discovered by posttreatment whole-body scintigraphy in 29 out of 246 (11.8%) patients. In patients with metastases, malignant thyroid nodules were located in the right lobe (14/123, 11.4%), left lobe (7/95, 7.4%), and isthmus (8/27, 29.6%). The prevalence of metastases was significantly higher in patients with DTC located in the isthmus, compared to other sites (χ(2) = 9.6, p = 0.002). CONCLUSIONS: Our data show for the first time that a location of a thyroid cancer in the isthmus is an additional risk factor for RAI avid metastatic disease in pT1a-pT1b DTC patients, regardless of the presence or absence of other risk factors.
