Post-operative neck ultrasound and risk stratification in differentiated thyroid cancer patients with initial lymph node involvement

OBJECTIVE: Cervical ultrasound (US) scan is a key tool for detecting metastatic lymph nodes (N1) in patients with papillary thyroid cancer (PTC). N1-PTC patients are stratified as intermediate-risk and high-risk (HR) patients, according to the American Thyroid Association (ATA) and European Thyroid Association (ETA) respectively. The aim of this study was to assess the value of post-operative cervical US (POCUS) in local persistent disease (PD) diagnosis and in the reassessment of risk stratification in N1-PTC patients. DESIGN: Retrospective cohort study. METHODS: Between 1997 and 2010, 638 N1-PTC consecutive patients underwent a systematic POCUS. Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of POCUS for the detection of PD were evaluated and a risk reassessment using cumulative incidence functions was carried out. RESULTS: After a median follow-up of 41.6 months, local recurrence occurred in 138 patients (21.6%), of which 121 were considered to have PD. Sensitivity, specificity, NPV, and PPV of POCUS for the detection of the 121 PD were 82.6, 87.4 95.6, and 60.6% respectively. Cumulative incidence of recurrence at 5 years was estimated at 26% in ETA HR patients, 17% in ATA intermediate-risk patients, and 35% in ATA HR patients respectively. This risk fell to 9, 8, and 11% in the above three groups when the POCUS result was normal and to <6% when it was combined with thyroglobulin results at ablation. CONCLUSION: POCUS is useful for detecting PD in N1-PTC patients and for stratifying individual recurrence risk. Its high NPV could allow clinicians to tailor follow-up recommendations to individual needs.