Is Stimulated Thyroglobulin Necessary after Ablation in All Patients with Papillary Thyroid Carcinoma and Basal Thyroglobulin Detectable by a Second-Generation Assay?

Changing Paradigm in Treatment of Differentiated Thyroid Cancer

Differentiated thyroid cancer is an indolent cancer with an excellent prognosis when treated adequately. The treatment algorithm is well established and standardized. Surgery followed by radio-iodine treatment has stood the test of time. In the last decade, the paradigm has slightly shifted with newer diagnostic approaches like stimulated thyroglobulin and anti-thyroglobulin antibodies impacting the treatment decisions. The diagnostic whole body radio-iodine scan has also got innovated with the introduction of r-TSH injection protocol wherein the scan is performed while the patient is on thyroxine thereby minimizing patient discomfort. The new RISK-based classification system has resulted in altered treatment algorithms by sub dividing patients into low-, intermediate-, and high-risk groups. There has also been identification of TWO new class of thyroid cancer patients-radio-iodine-resistant thyroid cancer and TENIS syndrome (thyroglobulin elevated negative iodine scan) patients. Both these groups posed major challenge to treatment and this resulted in incorporation of TARGETED THERAPY based on the mutations that occur in these TWO groups of patients. The introduction of Sorafenib and Lenvatinib has made significant impact on progression-free and overall survival of these patients. The introduction of THYROPET (124-I PET scan) is gaining momentum as an alternative to 123/131-I scans due to high-resolution images on PET scan increasing the detection sensitivity. All the above factors have resulted in paradigm shift in the management of differentiated thyroid cancer patients.

Response to Therapy Assessment in Intermediate-Risk Thyroid Cancer Patients: Is Thyroglobulin Stimulation Required?

Introduction: The 2015 American Thyroid Association (ATA) guidelines recommend response to therapy (RTT) assessment 1-2 years after initial treatment in differentiated thyroid cancer (DTC) patients to guide thyrotropin (TSH) goals and long-term follow-up. We hypothesized that data collected during the first 2 years of follow-up may be sufficient to determine RTT without thyroglobulin (Tg) stimulation. Materials and Methods: Patients treated with total thyroidectomy and radioiodine for intermediate-risk DTC, followed for >2 years, and had sufficient follow-up data were included. Data on Tg, ultrasound, scans, and long-term outcomes were collected. Results: One-hundred twenty patients met inclusion criteria, with 68% women and mean age 55 ± 15 years. Intermediate risk was due to lymph-node involvement (72%), extrathyroidal extension (51%), vascular invasion (12%), and high-risk histology (9%). At the end of follow-up of 7 ± 4 years, 26% had persistent disease (14% biochemical, 12% structural). According to the ATA RTT system (using stimulated-Tg), 56% had excellent RTT, of whom only 2% had disease at the end of follow-up. In the "nonstimulated" system (which includes basal Tg, post-¹³¹I therapy whole-body scan (TxWBS) for assessment of residual lymph-node metastases after surgery, and structural imaging studies), 57% had excellent response, of whom none had disease at the end of follow-up. Only eight patients (7%) were classified differently due to recombinant human thyrotropin stimulation (as either excellent or indeterminate response), with no difference in predictive value, with a receiver-operator characteristic area under the curve of 0.903 with Tg-stimulation and of 0.918 without. Conclusions: In patients with no evidence of disease during the first 2 years of follow-up, the addition of stimulated-Tg adds little prognostic information. We suggest the use of excellent RTT based on basal Tg together with TxWBS and structural imaging studies.

Can the basal serum thyroglobulin level be used to predict the recombinant human TSH-stimulated thyroglobulin level in differentiated patients with thyroid cancer?

This study investigated the correlation between basal thyroglobulin (Tg) and recombinant human thyroid-stimulating hormone (rhTSH)-stimulated Tg in differentiated patients with thyroid cancer, and sought to determine whether the basal Tg level predicts the rhTSH-stimulated Tg level.We retrospectively enrolled 177 patients with papillary thyroid cancer (mean age = 44 years; 50 males, 127 females) who received rhTSH before radioiodine therapy (RIT). Serum Tg levels were measured 7 days before the 1st rhTSH injection (basal Tg) and on the days of RIT (rhTSH-stimulated Tg). Patients were divided into 3 groups according to rhTSH-stimulated Tg cut-off levels of 2, 5, and 10 ng/mL. The correlation between basal Tg and rhTSH-stimulated Tg levels was assessed, and whether basal Tg was useful in predicting the rhTSH-stimulated Tg level was determined.A significant positive correlation was observed between basal and rhTSH-stimulated Tg levels (|rho| = 0.48, P < .0001). The basal Tg level had significant diagnostic ability in predicting an rhTSH-stimulated Tg level of 2 ng/mL or higher, and the optimal basal Tg level for this prediction was 0.3 ng/mL (AUC = 0.77, P < .0001). A basal Tg level of 0.5 ng/mL was optimal for predicting rhTSH-stimulated Tg levels of 5 ng/mL or higher (AUC = 0.81, P < .0001), and of 10 ng/mL or higher (AUC = 0.82, P = .0171).The basal Tg level was significantly correlated with the rhTSH-stimulated Tg level. If the basal Tg level is >0.3 or 0.5 ng/mL, then the rhTSH-stimulated Tg level can be expected to be sufficiently high to necessitate clinical examination.

Can the follow-up of patients with papillary thyroid carcinoma of low and intermediate risk and excellent response to initial therapy be simplified using second-generation thyroglobulin assays?

OBJECTIVE

In view of the low probability of recurrence, the cost-effective follow-up of patients with papillary thyroid carcinoma (PTC) of low or intermediate risk and excellent response to initial therapy represents a challenge. This study evaluated the cases of structural recurrence among these patients.

PATIENTS

The sample comprised 578 patients with PTC of low or intermediate risk, who were submitted to total thyroidectomy with or without (131) I therapy and exhibited an excellent response to initial therapy defined based on nonstimulated thyroglobulin (Tg) ≤0·2 ng/ml and negative neck ultrasonography (US).

RESULTS

Twelve patients (2%) showed structural recurrence. At the time when recurrence was 'confirmed', Tg elevation had not occurred in only two patients, one with lymph node metastases <1 cm detected by US and the other with pulmonary metastases. Antithyroglobulin antibodies (TgAb) were undetectable in both patients. The first alteration observed in patients with recurrence was Tg elevation in six patients, Tg elevation associated with suspicious US in three, and suspicious US in two. An increase in TgAb was not the first alteration in any of the patients. Among the 560 patients who continued to have Tg ≤ 0·2 ng/ml, US permitted the detection of only one neck recurrence. Measurement of TgAb did not detect any recurrence.

CONCLUSION

Our results confirm that in patients with PTC of low or intermediate risk an excellent response to initial therapy can be defined based on nonstimulated Tg ≤ 0·2 ng/ml. Follow-up consisting only of clinical examination and periodic measurement of Tg with a second-generation assay may be sufficient.