Papillary Thyroid Carcinoma Recurrence: Low Yield of Neck Ultrasound With an Undetectable Serum Thyroglobulin Level

The role of neck ultrasound in the follow-up of low- and intermediate- risk papillary thyroid cancer

Introduction

The optimal time for a neck ultrasound (US) in the follow-up of papillary thyroid cancer (PTC) after the first year is undetermined. We aimed to verify the utility of routine neck US in the surveillance of patients diagnosed with low- and intermediate-risk PTC with no evidence of disease at the one-year assessment.

Subjects and methods

We conducted a retrospective longitudinal study of patients with low- and intermediate-risk PTC with normal neck US, unstimulated serum thyroglobulin (Tg) < 1 ng/mL and negative anti-Tg antibodies at the one-year follow-up. Patients were divided into group 1 [undetectable Tg (<0.20 ng/mL)] and group 2 [detectable Tg but < 1 ng/mL]. The negative predictive value (NPV) of the one-year unstimulated Tg at the five-year and last follow-up visits was calculated.

Results

We included n = 88 patients in group 1 and n = 8 patients in group 2. No patient from group 1 presented suspicious US findings at the five-year evaluation [NPV: 100.0% (95% confidence interval (CI): 95.5%-100.0%)], and at the last visit, only one patient had developed a lymph node classified as suspicious [NPV: 98.8% (95% CI: 93.2%-100.0%); mean follow-up: 6.7 years]. In group 2, two patients' USs presented suspicious findings at the five-year evaluation [NPV: 75.0% (95% CI: 34.9%-96.8%)]. At the last visit, only one patient persisted with suspicious findings in the US [NPV: 87.5% (95% CI: 47.4%-99.7%); mean follow-up: 6.5 years].

Conclusion

Low- and intermediaterisk PTC with an excellent response to treatment at the one-year assessment can be safely monitored with regular unstimulated Tg assessments. Conclusions should not be drawn for Tg levels between 0.20-0.99 ng/mL.

Role of Sonographic Characteristics of Thyroid Bed Lesions Identified Following Thyroidectomy in the Diagnosis or Exclusion of Recurrent Cancer

Background US of the thyroid bed in patients with thyroid cancer often depicts small lesions, but it is unclear whether US characteristics of lesions can help predict cancer recurrence. Purpose To determine whether size or US features of lesions in the thyroid bed after thyroidectomy in conjunction with clinical features can help predict thyroid cancer recurrence. Materials and Methods With use of a US reporting database, all patients imaged between July 2006 and June 2016 with an indication of post-thyroidectomy follow-up were retrospectively identified. Recorded data included patient demographic characteristics; date of thyroidectomy; thyroid cancer type; presence, size, and US characteristics of thyroid bed lesions; and results of fine-needle aspiration (FNA). Images were reviewed for lesions that underwent FNA. The Fisher exact test was used for analysis. Results A total of 1885 patients (mean age ± standard deviation, 48 years ± 15; 1493 female patients) underwent 5732 US examinations. Most patients (1541 of 1885 [82%]) had papillary cancer. Overall, 3163 thyroid bed lesions were reported in 5732 US examinations (40.4%). More than half of these lesions (1860 of 3163 [58.8%]) had a maximum measurement of 6 mm or greater. FNA was performed in 144 of the 3163 lesions (4.6%), of which 61 (42.4%) were malignant, 33 (22.9%) were benign, and 50 (34.7%) were nondiagnostic. Five nondiagnostic lesions eventually proved malignant. Only the presence of punctate echogenicities in the lesion (28 of 61 malignant lesions [45.9%]; three of 33 benign lesions [9%]; 12 of 50 nondiagnostic lesions [24%]; P < .001) or the history of positive lymph nodes at thyroidectomy (44 of 61 malignant lesions [72.1%]; 10 of 33 benign lesions [30%]; 19 of 50 nondiagnostic lesions [38%]; P < .001) were associated with malignancy. Of 3019 thyroid bed lesions that did not undergo FNA, three were malignant and 2248 showed no growth at follow-up US ranging from 6 months to 10 years and are presumed benign. Of the 1303 lesions smaller than 6 mm, only two (0.2%) were malignant. Conclusion Small lesions are commonly found in the thyroid bed after thyroidectomy, and most are likely to be benign. Lesions smaller than 6 mm with no punctate echogenicities had a minimal risk for malignancy. © RSNA, 2021 See also the editorial by Grant and Malhi in this issue.

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.

Ultrasonography surveillance in papillary thyroid carcinoma patients after total thyroidectomy according to dynamic risk stratification

PURPOSE

To investigate the role of neck US surveillance in patients with papillary thyroid carcinoma (PTC) after total thyroidectomy according to dynamic risk stratification (DRS) based on response to initial therapy.

METHODS

This retrospective study included 812 patients with PTC who underwent total thyroidectomy with prophylactic central neck dissection from January 2003 through February 2007. The relative risk of recurrence/persistence according to DRS was evaluated with the multivariable Cox regression proportional hazard model.

RESULTS

There were 132 men and 680 women. The mean age at surgery was 45.2 years. Postoperative US was used for DRS. According to DRS, 676 patients had excellent response, 78 indeterminate response, 40 biochemical incomplete response, and 18 structural incomplete response to initial therapy. Neck US was performed during follow-up and detected locoregional recurrences in 21 patients (2.6%): 12 with excellent response, 2 with biochemical incomplete response, and 7 with structural incomplete response according to DRS. Only 1 patient (0.1%) with excellent response had a locoregional recurrence that exceeded 8 mm in its shortest diameter, which is the size cut-off for diagnostic US fine-needle aspiration in suspicious lymph nodes. This patient did not develop biochemical abnormalities during follow-up.

CONCLUSIONS

Postoperative neck US surveillance after total thyroidectomy with prophylactic central neck dissection is not essential in PTC patients who show excellent response to initial therapy. Future studies are needed to verify the role of US surveillance in patients who receive variable degrees of treatments.

Individualized Follow-Up Strategy for Patients with an Indeterminate Response to Initial Therapy for Papillary Thyroid Carcinoma

BACKGROUND

The concept of a dynamic risk-stratification scheme has been suggested for individualized management of patients with papillary thyroid carcinoma (PTC). However, there is no specified follow-up strategy for patients with an indeterminate response.

METHODS

This study evaluated 403 PTC patients who had an indeterminate response during the first 12-24 months after initial therapy. All patients underwent total thyroidectomy with radioactive iodine remnant ablation. Patients were further classified into three groups based on risk of structural persistence/recurrence: a Tg+ group (detectable thyroglobulin [Tg], regardless of antithyroglobulin antibody [TgAb] or imaging findings; 196 patients), a TgAb+ group (positive results for TgAb with undetectable Tg, regardless of imaging findings; 46 patients), and an Image+ group (nonspecific findings on neck ultrasonography or faint uptake in the thyroid bed on whole-body scan, with undetectable Tg and negative results for TgAb; 161 patients).

RESULTS

With a median of 9.6 years (interquartile range 7.7-11.2 years) of follow-up, 56 (14%) PTC patients had structural persistent/recurrent disease: 50 (89%) at locoregional sites and six (11%) at distant sites. The recurrence rate in Tg+, TgAb+, and Image + groups were 26.5%, 8.7%, and 0%, respectively. The median time to detection of structural persistent/recurrent disease from the initial thyroid surgery was 3.7 years (interquartile range 2.5-6.3 years). The optimal cutoff stimulated Tg level to predict structural persistent/recurrent disease was 3.1 ng/mL in the Tg+ group. This classification system revealed higher predictability of structural persistent/recurrent disease than the tumor-node-metastasis staging system and American Thyroid Association risk stratification (proportion of variation explained: 15.7% vs. 2.4% and 0.9%, respectively). Six (3%) patients with distant metastatic disease were all classified in the Tg+ group, and all had lung metastasis.

CONCLUSIONS

The findings suggest a more individualized follow-up strategy for patients with an indeterminate response. More careful evaluation, including early evaluation of distant metastasis, is necessary in patients with elevated Tg levels. However, for patients testing positive for TgAb or those with only nonspecific imaging findings, regular follow-ups of Tg and TgAb levels and neck ultrasonography are sufficient.