Natural History and Long Term Follow-Up of Incidental Thyroid Nodules on Computed Tomography Imaging.

Abstract

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 one ITN > =1cm.

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. 120 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 of150 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.