Endocrine Abstracts

Background: The last American Thyroid Association guidelines (ATA-2015) defined the risk of structural recurrence in patients with DTC cured after initial treatment and according to the initial histology. However, these data resulted from several studies including different patients with different kinds of treatment. We retrospectively evaluated a large population of patients with DTC, treated and followed in a tertiary referral center, with the aim to characterize the rate of structural recurrence, the clinical-pathological factors involved in the recurrence and to compare our results with those proposed by the ATA-2015.

Patients and Methods: We evaluated epidemiologic and clinical-pathologic data of 1331 consecutive patients between January 2010 and September 2012, followed at the Operative Unit of Endocrinology of the University Hospital of Pisa. Data were collected at the time of first ¹³¹I treatment after surgery for all patients, and thereafter during the follow-up according to the standard of care.

Results: At the first control after ¹³¹I treatment (median time 8 months), 36 patients (2.7%) were lost at follow-up and 82 patients (6.2%) showed a structural incomplete response and for this reason were excluded from the study. In the remaining (n = 1213) who showed an excellent, indeterminate, or biochemical incomplete response, only 34 patients (2.8%) (Group A) showed a structural recurrence during the follow-up (median 7 years). Compared to the patients who did not show any structural recurrence (Group B), patients of group A showed more frequently larger tumor size (> 4 cm), aggressive histology, minimal extrathyroidal extension, vascular invasion and a more advanced TNM stage. When compared with ATA-2015, the overall recurrence rate in our group is significantly lower, both if considering the histologic ATA-2015 categories and when classifying patients in three groups according to initial histology and rate of recurrence reported (≤ 5%, 6-20%, > 20%).

Conclusions: In a large population of DTC patients without evidence of structural disease after the initial treatment, treated and followed with a uniform modality over time, the structural recurrence rate is a rare event (2.8%). However, several clinical and histologic factors were significantly associated with the risk of structural recurrence. The recurrence rate, in this series was lower than that proposed by ATA-2015. One possible reason is that these patients were followed-up at the same tertiary referral center with the same clinical strategy.