Repeat Ultrasonography in the First Years after Therapy with Radioiodine Is Not Necessary in Most Patients with Papillary Thyroid Carcinoma when Postoperative Ultrasonography Is Negative: A Reduction of Costs and False-Positives

Natural history, predictive factors of apparent disease (structural or biochemical) and spontaneous excellent response in patients with papillary thyroid carcinoma and indeterminate response to initial therapy with radioiodine

BACKGROUND

About 20% of patients with papillary thyroid carcinoma (PTC) submitted to total thyroidectomy followed by radioactive iodine (RAI) exhibit an indeterminate response to therapy. The aim was to evaluate the natural history, predictive factors of apparent disease (structural or biochemical), and spontaneous excellent response in patients with PTC and an initial indeterminate response to RAI therapy defined based on unstimulated Tg (u-Tg).

METHODS

We evaluated 164 patients who were initially treated with total thyroidectomy and RAI and who had an indeterminate response to therapy (u-Tg between 0.2 and 1 ng/ml, undetectable anti-Tg antibodies [TgAb], and neck ultrasonography [US] without anomalies). None of the patients received empirical therapy with RAI. The patients were followed up for 24 to 144 months (median 72 months).

RESULTS

Apparent disease occurred in 16 patients (9.7%), including 13 with structural disease and 3 with u-Tg elevation > 1 ng/ml, but no tumor was detected by the imaging methods (biochemical disease). A higher frequency of disease was observed in patients with >3 lymph node metastases (LNM) and initial u-Tg >0.35 ng/ml. The frequency was only 2% among patients with ≤3 LNM and u-Tg ≤0.35 ng/ml and 9.7% among patients with > 3 LNM or u-Tg >0.35 ng/ml, while the frequency was 27% in patients with >3 LNM and u-Tg >0.35 ng/ml. In the absence of any additional therapy, u-Tg was <0.2 ng/ml (excellent response) in the last assessment in 70 patients (42.7%). Only initial u-Tg was associated with a higher probability of spontaneously achieving an excellent response: 40/72 patients (55.5%) with u-Tg ≤0.35 ng/ml versus 30/92 patients (32.6%) with u-Tg >0.35 ng/ml.

CONCLUSIONS

A minority of patients with PTC and an initial indeterminate response to RAI defined based on u-Tg develop apparent disease (structural or biochemical) and many spontaneously achieve an excellent response. The risk of disease can be refined based on parameters such as the extent of lymph node involvement and initial Tg concentration.

Thyroglobulin Antibodies as a Prognostic Factor in Papillary Thyroid Carcinoma Patients with Indeterminate Response After Initial Therapy

The clinical outcome of papillary thyroid carcinoma (PTC) patients with an indeterminate response after initial therapy is reported to be intermediate, between incomplete and excellent responses. This study evaluated the outcomes of PTC patients with indeterminate response after initial therapy. It was further determined whether the indeterminate findings predicted outcomes more precisely. Patients were further classified into 3 groups based on risk of structural persistence/recurrence: Tg group: detectable thyroglobulin, negative antithyroglobulin antibody, regardless nonspecific imaging findings; TgAb group: positive antithyroglobulin antibody, regardless thyroglobulin levels and nonspecific imaging findings, and Image group: nonspecific findings on neck ultrasonography or faint uptake in the thyroid bed on whole-body scan, undetectable thyroglobulin and negative antithyroglobulin antibody. Sixty-six patients aged 44.1±12.7 years were studied, of whom 58 (87.9%) were females. All patients underwent total thyroidectomy, and 52 patients (78.8%) received radioiodine. After 5.7 years (P25-75 2.6-9.75 years) of follow-up, most patients (89.4%) were reclassified as having an excellent response or remained in the indeterminate response to therapy. Structural recurrence/persistence disease was detected in 7 (10.6%) patients. The persistence/recurrence rate in groups were as follow: Tg, 2.63%; TgAb, 31.25%; Image, 8.3% (p=0.007). The 10-years disease-free survival rate in the TgAb group was significantly reduced (p=0.022). Our results suggest that patients with PTC and indeterminate response due to positive serum antithyroglobulin antibody have more risk of development of structural disease. These findings suggest a more individualized follow-up strategy for patients with an indeterminate response.

Unstimulated high-sensitive thyroglobulin is a powerful prognostic predictor in patients with thyroid cancer

Background Differentiated thyroid carcinoma (DTC) has an excellent prognosis and the role of high-sensitive thyroglobulin measured during levothyroxine (ON-T4 hs-Tg) testing to discriminate patients with structural from not-evidence of disease (SED and NED, respectively) has been investigated. We conducted a systematic review and meta-analysis evaluating the performance of ON-T4 hs-Tg in two clinical scenarios considering its negative predictive value (NPV) as primary outcome: (1) diagnostic performance of Tg when undetectable value and NED status are simultaneously demonstrated; (2) prognostic performance of undetectable Tg in predicting NED in the subsequent follow-up. Methods This systematic review and meta-analysis were registered on PROSPERO (CRD42019125092). PubMed, Scopus, CENTRAL and Web of Science were searched until February 12, 2019. Original articles reporting data on SED/NED in patients with detectable/undetectable ON-T4 hs-Tg were selected. Summary operating points were estimated using a random-effects model. Results Out of 1413 retrieved papers, 10 studies evaluating 1796 patients were included. Participants were outpatients diagnosed with DTC, treated with near-total (NTx) or total thyroidectomy (TTx) with or without radioactive iodine (RAI). The NPV of ON-T4 hs-Tg for diagnostic and prognostic performance was 99.4% (95% CI 98.9-99.9; I2 = 13%) and 99.4% (95% CI 98.8-100; I2 = 0%), respectively. Conclusions Our findings show that ON-T4 hs-Tg is an excellent diagnostic tool and prognostic factor to rule-out SED. A high level of evidence is provided to decrease the intensity and frequency of follow-up in those DTC patients having undetectable high-sensitive Tg.