Endocrine Abstracts

Background: Cervical lymph node metastases at histology are common findings in differentiated thyroid cancer (DTC); however, their impact on clinical outcome is debated.

Material and method: 1332 DTC patients, performed the first ¹³¹ I treatment between January 2010 and September 2012 and were divided into 2 groups: absence (Nx/N0) or presence (N1) of lymph node metastases at histology. The latter group was further split in central compartment (N1a) or latero-cervical compartment (N1b) metastases. Clinical outcome, according to 2015 ATA guidelines, was defined at: post-operative and post-¹³¹ I (median time from surgery: 6 months), first evaluation after ¹³¹ I (median time from ¹³¹ I: 8 months) and at last evaluation (median time since ¹³¹ I: 83 months).

Results: 1064 (79.9%) patients were in the Nx/N0 group and 268 (20.1%) in the N1 group. N1 patients were more frequently males (35.8 vs 27.3%, P<0.01) and younger (median age 40 vs 47, P<0.01). Several pathological features were prevalent (P<0.01) in the N1 group: multifocality (63.4 vs 46.8%), mETE (67.9 vs 24.6%), vascular invasion (28 vs 8.9%) and intermediate ATA risk (94.8 vs 36.5%). The incomplete structural response rate was higher in N1 group, in all times of follow-up (P<0.01), despite N1 patients significantly experienced higher ¹³¹ I activities and more neck re-operation. N1b (n=142, 53%) patients, compared to N1a (n=126, 47%), had higher prevalence of mETE (74.6 vs 59.5%, P<0.01) and vascular invasion (33.1 vs 22.2%, P<0.05) and lower histological thyroiditis (21.1% vs 35.7, P<0.01). Regarding treatment, N1b patients experienced higher ¹³¹ I activities and more neck re-operation. Structural incomplete response rate was significantly higher at post-operative (16.2% vs 6.3%), post-¹³¹ I (26.1 vs 8.7%) and at first assessment after ¹³¹ I (24.3% vs 9.6%). Conversely, at the last evaluation, significance was not reached (17.9% vs 10.4%, P=0.09).

Conclusions: Cervical lymph node metastases at histology are associated with more aggressive features in DTC. Despite the higher activity of the ¹³¹ I administered and the more frequent surgery on neck, the N1 patients showed a higher structural incomplete response rate at each time of the follow-up. N1b patients, compared to N1a, experienced more frequent and aggressive treatments during the follow-up with higher incomplete structural response rate.