Endocrine Abstracts

Introduction: MTC is a rare neuroendocrine tumor arising from thyroid parafollicular cells. After initial treatment, patients should be divided according to their clinical status in cured, biochemical persistence (BIO) and structural persistence (STR) of the disease. Concerning BIO patients less is known about the structural disease appearance rate and the time elapsed between the first evaluation after surgery and the appearance of structural disease.

Method: We retrospectively reviewed data of 592 consecutive patients with sporadic MTC, followed at the Endocrine Unit of the University Hospital of Pisa, from 2000 to 2018. After surgery, all patients were reclassified according to clinical, biochemical [basal (bCT) or stimulated (sCT) calcitonin], neck ultrasound and, whenever indicated, other imaging procedures. When bCT or sCT was above upper normal level according to gender thresholds, without evidence of structural disease, patients were considered BIO.

Results: After a median time of 5 months after surgery (IQR 3-8), 132/592 (22.3%) patients showed BI0. Among these, 89/132 (67.4%) and 43/132 (32.6%) patients were considered BIO for elevated bCT or sCT, respectively. Median time follow-up of the BIO group was 103 months (IQR 50.5-152.5). The appearance of structural disease occurred in 60/132 (45.5%) patients, after a median time of 37.5 months (IQR 16-61.5). In patients who were considered BIO for the presence of elevated bCT, the appearance of structural disease was more frequent than those with a positive sCT (56.2% vs 23.3%, P<0.001). This finding was still more evident when comparing patients with bCT > 150 pg/ml to those<150 pg/ml (82.6% vs 37.6%, P<0.001). Neck was the most common site of structural disease appearance (41/60, 68.3%), followed by bone (9, 15%), liver (8, 13.3%), lungs (6, 10%) and mediastinal lymph nodes (5, 8.3%). Half of patients in whom structural disease appeared (30/60 – 50%), were submitted to other treatments and of these, 11/30 (36.6%) started systemic therapies.

Conclusions: In our large cohort of sporadic MTC patients with BIO, about half of them showed the appearance of a structural disease, prevalently located in the neck, after a median time of 3 years of follow-up. Patients with elevated bCT at first evaluation, particularly those with bCT > 150 pg/ml, had the higher risk of structural disease appearance.