Endocrine Abstracts

Background: Active surveillance (AS) has been widely accepted as a safe option in the treatment of low risk papillary thyroid microcarcinoma (PTMC) in recent years on the basis that its prognosis is not inferior to immediate surgery. However, clinicians as well as patients are still hesitant in actually choosing AS over immediate OP as treatment. Our aim was to investigate the factors in choosing treatment options in low risk PTMC.

Method: Seoul National University Bundang hospital (SNUBH) is a participant of Multicenter Prospective Cohort Study of Active Surveillance on Papillary Thyroid Microcarcinoma (MAeSTro) which started in 2016. Adults aged more than 18 years who visited SNUBH with newly diagnosed thyroid nodules between May 1, 2016 and October 5, 2018 were recruited (n =1923). Patents with papillary thyroid microcarcinoma 1 cm or less, with US guided fine needle aspiration (FNA) or Core needle biopsy (CNB) results of suspicious of malignancy or malignancy, Bethesda category V or VI were enrolled (n =901).

Results: 692 patients (538 Female 77.7%) with low risk PTMCs with a median age of 43 years (range 18–80) were analyzed. Patients having Graves’ disease requiring operation or RAI (n =1) or high risk features of suspected organ involvement (n =155), clinical or pathological Lymph node involvement or distant metastasis (64), or poorly differentiated histology or variant with poor prognosis (n =0) were excluded from analysis. AS was selected in 191 (27.6%) and OP in 501(72.4%) patients. There was no difference in the proportion of females in the AS and OP groups (74.3% vs 79.0% P = 0.184). The mean of the initial ultrasonic maximum diameter was 0.71 cm (range 0.2-1.0 cm, median 0.7 cm). The initial size of the nodules was larger in the OP group than in the AS group (mean, 0.72 cm vs 0.67 cm P = 0.000). The mean of the initial size of the nodules was larger in the 70s and 80s (n =11, 0.90 cm) compared to the rest of the age group showing, 10s to 20s(n =53): 0.73 cm, P = 0.179; 30s(n =199): 0.71 cm, P = 0.194; 40s(n =211): 0.70 cm, P = 0.210; 50s(n =160): 0.71 cm, P = 0.195; 60s(n =58): 0.70 cm, P = 0.216; (n =11): 0.90 cm). The older groups tended to select AS more than the younger groups, especially those over the age of 50 (24.0 % vs 34.9%, P = 0.002). 90.3% of the low-risk PTMC patients who were enrolled in MAeStro and 4.5% of those who were not chose AS.

Conclusion: AS was more easily selected when enrolled in the prospective study comparing between AS and immediate surgery in low-risk PTMC patients, MAeSTro. Multidisciplinary management through study enrollment was an important factor for the selection of AS.