L. Zhou1, K. Patel1 1New York University School Of Medicine,Endocrine Surgery,New York, NY, USA
Introduction:
The Afirma® Gene Expression Classifier (AGEC) has been designed to identify benign thyroid nodules among those classified as cytologically indeterminate with a negative predictive value of 94%–95%. This test therefore has the potential of avoiding unnecessary surgery on cytologically indeterminate nodules which are likely to be benign. The objective of this study was to examine the impact of AGEC on the management of thyroid nodules at a single institution and appreciate the importance of how institutional malignancy rates may affect clinical decision making and patient counseling.
Methods:
A retrospective cohort analysis of all patients treated by the authors with thyroid nodules classified as Bethesda category III or IV, who had AGEC testing. Only patients with cytologic diagnosis, AGEC and final pathology were included. Cytology was categorized according to the Bethesda classification system. The dataset was analyzed to determine the benefit of AGEC testing in our patient population.
Results:
A total of 54 patients were included in the study. 44 had initial cytologic diagnosis categorized as Bethesda III and 10 were categorized as Bethesda IV. Of the 54 GECs performed, 15 were benign and 39 were suspicious. 13/15 (86.7%) patients with benign GEC testing opted for close observation and 2/15 (13.3%) opted for surgery, both had benign disease on final pathology. Surgery was avoided in 13/54 (24%) patients. 23/39 (59.0%) patients with suspicious GEC testing have had surgery and their pathology is as follows: 11/23 (47.8%) benign, 5/23 (21.7%) papillary thyroid cancer (PTC), and 7/23 (30.4%) follicular variant PTC. The PPV of AGEC “suspicious” in our patient population is 52.2%. The historical prevalence of malignancy amongst cytologically indeterminate lesions (Bethesda III and IV) at NYU is 35%. Based on this, the NPV of AGEC at our institution is closer to 91%.
Conclusion:
Malignancy rates in cytologically indeterminate thyroid nodules vary widely across institutions. Utilization of the AGEC helped avoid surgery in 24% of patients with cytologically indeterminate thyroid nodules. However, given our center’s higher prevalence of malignancy in indeterminate nodules, slightly higher PPV and slightly lower NPV were observed compared to previously published rates. This information must be taken into consideration when making clinical decisions and counseling patients in regards to AGEC testing.