SAT-451 Acromegaly and Thyroid Cancer

Introduction Acromegaly is associated with higher morbidity and mortality due to malignant neoplasms. However, data on the incidence and evolution of thyroid cancer in acromegaly is controversial. Objectives: To describe the clinical and biochemical characteristics of a group of acromegalic patients with differentiated thyroid carcinoma (DTC). Identify any predicting factor for DTC evolution. Analyze risk of recurrence (RR), initial response to treatment and response at the end of follow-up (RFU), comparing the outcomes with non-acromegalic patients with DTC. Patients and methodsRetrospective, multicenter study of 16 acromegalic patients with DTC. Acromegaly control or remission was defined with an IGF-1 ≤1 ULN with or without medical treatment (MT) respectively. AJCC Staging System 8th Edition was used for TNM staging, and the initial RR, initial response and RFU were defined according to ATA Guidelines 2015. As a control group, 56 patients with DTC without acromegaly were selected. Statistical analyses were done using SPSS Statistics 2.0. Results Median age of patients at the diagnosis of acromegaly was 44 years (range 12-69). Delay in diagnosis of acromegaly was a median of 2.5 years (range 0.5-10). Basal mean IGF-1 level was 3.2 ± 1.2 xULN. Surgery was performed in 85.7%. Post surgically, the best mean IGF-1 was 1.24 ± 0.34 xULN. Control with MT was achieved in 80%, with a median time to control since diagnosis of 21 months (6-132). Mean age at CDT diagnosis was 46.5 years (18-69). No patient had personal history of cervical irradiation. Most patients (86.7%) had normal thyroid function tests At the moment of diagnosis of DTC 62.5% of the patients had active acromegaly, IGF-1 of 2.5 ± 1.4 xULN. Median time from CDT diagnosis to acromegaly control was 1 year (0.5-7). Mean DTC tumor diameter of the bigger lesion was 13.7 ± 7.4 mm, being multifocal in 40% of the cases. All were papillary carcinoma, one case an aggressive variety. In 6/15 lymph node dissection was done, 50% with metastasis. One patient had distant metastasis. Radioiodine ablation was given to 87.5%, mean dose 115 ± 64.5 mCi. Twelve of the patients were stage I, 3 stage II and 1 IVb. Initial RR was low in 14/16, intermediate in 1 and high in 1 patient. RFU was: 13/15 with no evidence of disease, 1 patient with biochemical incomplete response and 1 with structural incomplete response, on average at 47.7 ± 33.3 months of FU. No statistically significant correlations were found between characteristics of the acromegalics and DTC outcomes. When comparing response on FU between acromegalics and controls no statistically significant differences were found. Conclusions The acromegalics with DTC had a low initial RR, that could be related to an early diagnosis of DTC (anticipated bias). We did not find any predisposing factor for unfavorable evolution. When comparing with the control group, we can conclude that DTC in acromegaly does not have a worse evolution.