Patients with familial adenomatous polyposis (FAP) have an increased risk of thyroid nodular disease. Previous studies demonstrated that screening thyroid ultrasound (US) will allow detection of nodules in 38% and thyroid cancer in 2.6% of patients. The aim of this study is to define the value of serial US evaluation at identifying disease progression in patients with FAP.

Retrospective review from 2008-2023 at a single referral center. All patients with FAP and screening thyroid US were included. Patient demographics, initial US characteristics, follow-up regarding the development of new nodules and cancer were assessed using a Kaplan-Meier analysis.

A total of 556 patients underwent screening. 51% were male. Median age at first screening was 38 years old. 81% underwent longitudinal follow-up for a median length of 7 years. At initial screening, 169 patients (30%) had nodules. For patients with normal baseline US, 14% developed a nodule overtime. A total of 20 patients (3.6%) were diagnosed with thyroid cancer. The cumulative incidence of initial and subsequent cancer was 4% by 5-years and 6% by 10-years, while the cumulative incidence of thyroid nodules was 40% and 48%, respectively.

Based on the Kaplan-Meier analysis, ongoing longitudinal screening is warranted for patients with FAP as they are prone to thyroid cancer and nodule development overtime even when presenting with a baseline normal US. Additionally, these data demonstrate a slow development of thyroid cancer from a normal US, thus it is reasonable to consider selectively extending the screening interval for this population.