THYROID NODULE GROWTH AS A PREDICTOR OF MALIGNANCY

Natural history and long-term follow-up of incidental thyroid nodules on CT imaging

OBJECTIVES

Incidental thyroid nodules (ITNs) are found in up to 25% of CT scans. Increased use of cross-sectional imaging has contributed to the increased incidence of thyroid cancer worldwide. ITNs pose a management dilemma since nodule malignancy rate is 5%-15% but most cancers are indolent and prognosis in differentiated thyroid cancer is excellent. Study aims are to determine prevalence of ITNs ≥1 cm on CT scans, evaluate reporting practices, assess for emergence of clinically evident thyroid cancer during 13-year follow-up and assess interim nodule growth and clinical outcomes in nodules that were further investigated.

METHODS

Direct image review of 1499 consecutive CT scans that included the thyroid, performed during January 2009 in a large NHS health board was performed. Clinical data up to January 2022 was analysed in 150 patients with at least 1 ITN ≥1 cm.

RESULTS

ITN prevalence was 11% with mean patient age 70 years and mean nodule diameter 17.5 mm. 30% of ITNs were mentioned in the CT report. During the follow-up period 11% proceeded to thyroid ultrasound, 5% fine needle aspiration, and 2% diagnostic hemithyroidectomy with no thyroid malignancy found. One hundred twenty patients (80%) were deceased by the study endpoint, none from thyroid malignancy. No patients presented with clinically evident thyroid malignancy during follow-up.

CONCLUSIONS

None of 150 ITN cases developed clinically evident thyroid malignancy in a 13-year follow-up period with 80% of patients deceased by the study endpoint from non-thyroid causes.

ADVANCES IN KNOWLEDGE

This would suggest that ITNs detected on CT do not require further investigation unless malignant appearances or significant clinical concern for thyroid malignancy.

Changes in the Volume and Diameter of Benign Thyroid Nodules: A 10-Year Follow-Up Study

Background: The incidence of asymptomatic thyroid nodules has risen enormously, with > 90% being benign. Despite limited long-term data, significant nodule growth (SNG) is common. Guidelines recommend cytology reevaluation if SNG occurs. Our study aimed to identify the rate and factors associated with SNG, compare diameter and volume-based assessments, and examine the association between SNG and malignancy risk over the long term (10 years). Methods: The retrospective cohort study, conducted at Ankara University, School of Medicine, Department of Endocrinology and Metabolism, included 732 nodules from 376 euthyroid patients, all monitored over a 10-year period by the same experienced sonographer, with evaluations at baseline, 5th and 10th years. The nodules were cytologically benign and/or sonographically in the low-to-intermediate risk category. Size changes at the 5th and 10th years were considered significant if there was a 20% or 2 mm increment in two diameters according to diameter-based criterion (DBC) or 50% increment in volume-based criterion (VBC) designed by the ellipsoid formula. Generalized linear mixed-effects models were used to account for the clustered data structure and analyze factors affecting nodule growth. Nodule growth was the dependent variable, while sex, age at diagnosis, initial TSH level, total nodule count, nodule volume, echogenicity, and localization were independent variables. Results: At the 5th and 10th years, SNG frequencies were higher when calculated using VBC [27.7% (n = 203) and 44% (n = 321), respectively] compared with DBC [19.1% (n = 140) and 35% (n = 256), respectively], with the differences being statistically significant (McNemar test, p < 0.01). Factors associated with SNG included being younger than 45 years of age (VBC OR = 1.704, CI = 1.227-2.366, p = 0.002; DBC OR = 1.913, CI = 1.379-2.656, p < 0.001), having higher number of nodules (VBC: OR = 1.171, CI = 1.061-1.291, p = 0.002; DBC: OR = 1.147, CI = 1.040-1.265, p = 0.006), and having smaller nodule volume (VBC: OR = 0.870, CI = 0.806-0.940, p < 0.001; DBC: OR = 0.912, CI = 0.850-0.978, p = 0.010). Thyroid cancer was diagnosed in four original nodules (0.5%), whereas the malignancy rate in biopsies performed was 1.4% (n = 4). Conclusions: In long-term follow-ups of sonographically and/or cytologically benign thyroid nodules, SNG is not rare. Growth is more likely in younger patients, those with higher number of nodules and smaller nodules. In the follow-up of nodule size, VBCs yield augmented results compared with DBCs. However, malignancy is quite rare in growing nodules. Therefore, adopting flexible long-term follow-up protocols appears to be practical for benign nodular thyroid disease.

Management of Indeterminate Thyroid Nodules: A Model Comparing Surgery, Molecular Testing, and Observation

OBJECTIVE

Optimal management of indeterminate nodules remains a controversial area of endocrine surgery. The purpose of this study is to compare observation, molecular testing, and immediate thyroid surgery for the management of Bethesda Classes III and IV nodules in patients age 50 to 90 years.

STUDY DESIGN

A decision analysis was performed from April 22, 2021, to September 29, 2023, using a Markov model constructed with TreeAgePro 2023. Model variables and ranges were selected based on literature review data.

SETTING

TreeAgePro.

METHODS

A 1-way sensitivity analysis was performed to evaluate the age threshold at which each management pathway, immediate thyroid surgery, additional molecular testing, or observation, would be favored. A Monte Carlo probabilistic sensitivity analysis was performed 5 times with model patients assigned starting ages of 50, 60, 70, 80, and 90 years to assess how age at diagnosis would impact model results. Outcomes were measured with quality-adjusted life-years and accounted for perioperative complications including permanent recurrent laryngeal nerve injury, permanent hypoparathyroidism, and medical complications.

RESULTS

In the study models, molecular testing was more beneficial than surgery and observation across all ages. The age threshold at which observation became more beneficial than surgery as the next best option was 83.1 years. However, the clinical difference between all 3 treatment algorithms was relatively minimal.

CONCLUSIONS

Decision-making regarding indeterminate thyroid nodules is complex. Given the clinically similar results across all 3 treatment algorithm, this study reinforces that treatment modalities should be individually tailored and based on shared physician-patient decision making.

Identifying and Predicting Diverse Patterns of Benign Nodule Growth

CONTEXT

The natural history of benign thyroid nodules is typically characterized by slow growth and minimal risk of malignant transformation. Available data have, to date, been unable to elucidate the diversity of benign nodule growth patterns over time nor predictive of which patients follow which pattern.

OBJECTIVE

We aimed to better define the diverse patterns of benign nodule behavior and their predictors.

METHODS

We prospectively studied 389 consecutive patients with solitary, solid, cytologically benign thyroid nodules ≥1 cm and follow-up ultrasound for at least 4 years. Demographic, sonographic, biochemical data were collected at initial evaluation, and subsequent growth patterns were identified over the follow-up. Predictors of growth at initial evaluation and 3 years of follow-up were defined.

RESULTS

The mean (±SD) follow-up was 7.7 (±2.7) years. Three distinct growth patterns were identified: A) stagnant nodules with average growth rate < 0.2 mm/year; B) slow-growing nodules with a rate 0.2 to 1.0 mm/year; and C) fast-growing nodules increasing > 1.0 mm/year. Fast-growing nodules represented 17.2% of the cohort, and were more frequent in patients younger than 50 years (OR 2.2 [1.2-4.1], P = 0.016), and in larger nodules (2.0-2.9 cm, OR 3.5 [1.7-7.1], P = 0.001; >3.0 cm, OR 4.4 [1.8-10.4], P = 0.001 vs reference 1-1.9 cm). In a multiple regression model, nodule growth at 3 years at an average growth rate over 0.2 mm/year over 3 years since initial evaluation was an independent predictor of longer-term fast nodule growth, even after adjusting for age, biological sex, TSH level, and nodule size (P < 0.001).

CONCLUSION

The natural history of benign nodule growth is diverse, with over 80% of nodules demonstrating minimal to no growth long-term. Nearly 20% of cytologically benign nodules may exhibit a fast, continued growth pattern, which can be predicted by the 3-year growth rate pattern. These findings can help inform decision making for tailored benign nodule follow-up and monitoring.

2021 Korean Thyroid Imaging Reporting and Data System and Imaging-Based Management of Thyroid Nodules: Korean Society of Thyroid Radiology Consensus Statement and Recommendations

Incidental thyroid nodules are commonly detected on ultrasonography (US). This has contributed to the rapidly rising incidence of low-risk papillary thyroid carcinoma over the last 20 years. The appropriate diagnosis and management of these patients is based on the risk factors related to the patients as well as the thyroid nodules. The Korean Society of Thyroid Radiology (KSThR) published consensus recommendations for US-based management of thyroid nodules in 2011 and revised them in 2016. These guidelines have been used as the standard guidelines in Korea. However, recent advances in the diagnosis and management of thyroid nodules have necessitated the revision of the original recommendations. The task force of the KSThR has revised the Korean Thyroid Imaging Reporting and Data System and recommendations for US lexicon, biopsy criteria, US criteria of extrathyroidal extension, optimal thyroid computed tomography protocol, and US follow-up of thyroid nodules before and after biopsy. The biopsy criteria were revised to reduce unnecessary biopsies for benign nodules while maintaining an appropriate sensitivity for the detection of malignant tumors in small (1-2 cm) thyroid nodules. The goal of these recommendations is to provide the optimal scientific evidence and expert opinion consensus regarding US-based diagnosis and management of thyroid nodules.