Lower Rates of Residual/Recurrent Disease in Patients with Incidentally Discovered Thyroid Carcinoma

Program: Abstracts - Orals, Poster Previews, and Posters
Session: SAT 270-310-Thyroid Neoplasia (posters)
Saturday, April 2, 2016: 1:15 PM-3:15 PM
Exhibit/Poster Hall (BCEC)

Poster Board SAT 297
Jawairia Shakil*1, Mohammed Zafer Ansari2, Jett Brady3, Jiaqiong Xu4 and Richard J Robbins1
1Houston Methodist Hospital, Houston, TX, 2Houston Methodist Sugar Land Hospital, Houston, TX, 3Houston Methodist Hospital, 4Houston Methodist Research Institute, Houston, TX
Abstract: The incidence of thyroid cancer (TC) has tripled in the last 30 years. However, death rates are stable. Incidentally discovered (ID) TC makes up a significant percentage of the new TC cases. Hypothesis: We hypothesized that IDTC is less aggressive and carries a better progression-free survival than clinically apparent (CA) TC. Methods: With IRB approval, a retrospective review of TC patients diagnosed between 2005 and 2014 at Houston Methodist was performed. Demographics, tumor size, histology, lab studies and presence of metastasis were collected.  Patients were staged according to AJCC, 7th edition.  IDTC was defined as: 1) histologically proven TC initially discovered on imaging not intended for evaluation of the thyroid; and 2) TC discovered after thyroidectomy for benign thyroid diseases. CATC was defined as TC discovered due to clinical signs or symptoms, or imaging done specifically to evaluate thyroid anatomy. Residual or recurrent (R/R) TC was defined structurally based on TIRADS ultrasound criteria. A serum Tg level confirming R/R disease was defined as > 5 ng/ml, in the setting of a suppressed TSH and a negative neck US.  Patient with anaplastic or medullary TC, < 3 Tg measurements or < 2 neck US exams were excluded. P-values were based on t-test for continuous variables, Mann-Whitney for skewed continuous variables, and Fisher’s exact test for categorical variables. Two-sided log rank tests defined significance. Univariate and multivariate analysis was performed to identify risk factors for recurrence. Results: 172 patients met inclusion criteria: 46 were ID and 126 were CA. Histology: papillary TC (n=160) follicular TC (n=10) and Hurthle cell TC (n=2). ID and CA had similar demographics and tumor characteristics. ID had fewer initial positive lymph nodes and were older. ID patients were more likely to be male, to have lower stage, and smaller tumors. Median follow-up time was 27 months (range: 6-348 months). At study closure, R/R status in the ID group was 6.7% compared to 20.8% in the CA group (p=0.04). Of the 28 individuals who had R/R disease, 3 were ID and 25 were CA (P=0.04). CA patients had recurrences out to 23 years, while no new recurrences were seen in the ID group after the initial 6 months. R/R disease was significantly higher in the CA group and in those with higher AJCC stage. Larger tumor size, TgAb positivity, and lymph node positivity were also significantly associated with final positive R/R status. On Kaplan-Meier analysis, there was a non-significant (P= 0.08) trend for longer progression-free survival in the ID group Conclusions:ID patients have more favorable initial histology and a significantly lower recurrence rates than CATC. If confirmed, we should consider approaching ID patients with less aggressive initial therapy and less invasive long-term surveillance.

Nothing to Disclose: JS, MZA, JB, JX, RJR

*Please take note of The Endocrine Society's News Embargo Policy at https://www.endocrine.org/news-room/endo-annual-meeting/pr-resources-for-endo

Sources of Research Support: Fellowship support for JS and MZA from Houston Methodist and CMS