Endocrine Abstracts

Introduction: Follicular thyroid cancer (FTC) accounts for 12% of differentiated thyroid cancers (DTC). It is frequently complicated by bone metastasis (BM), which impact quality of life (QOL) and decreases the 10-year survival rate to 13-21%.

Case Report: A 53-year-old woman followed at the Pain Clinic for over 10 years for lower back pain, had been operated three years before due to lumbar disc herniation. Pain relapsed one year after surgery and was resistant to analgesics. On physical examination (2010) a right thyroid mass and lower-extremity hypoesthesia were noted. Spine CT scan documented a 60x98 mm lytic mass at left pelvis and sacrum. Core biopsy revealed FTC with positivity for thyroglobulin (Tg) and TTF1. Thyroid ultrasound showed a bulky right thyroid nodule and suspicious right laterocervical lymph nodes. Laboratory tests revealed normal thyroid function, Tg 30334 ng/ml and negative TgAtbs. Thoracic CT documented pulmonary micrometastasis. Total thyroidectomy with cervical lymphadenectomy was performed. Histopathology showed a 7 cm widely invasive FTC with extra-thyroidal extension and lymph node metastases. Six weeks post-surgery Tg was 74560 ng/ml (TSH 8.9 uUI/ml). Within five years, she received four radioactive iodine (RAI) treatments with post-RAI scans demonstrating 131-I avid metastasis. After the second RAI, Tg dropped to 513 ng/ml, but TgAtb became positive. A debulking surgery with sacrum stabilization was also performed. Lenvatinib (LVT) was started seven years after diagnosis, due to imaging and biochemical evidence of metastatic progression, despite suppressive levothyroxine therapy and cumulative 131-I 29.7 Gbq. The dosage was reduced from 24 to 20 mg/day due to diarrhea. Arterial hypertension and anorexia developed and were pharmacologically controlled. She had good clinical and biochemical response (Tg decreased and stabilized; TgAtbs decreased and became negative). Thoraco-abdominal CT and spine MRI showed no significant signs of progression. Lumbar pain was controlled with opioids. After 1.5 years since LVT, there was pulmonary metastasis progression, despite biochemical stability. After an additional two years since LVT, she had substantial biochemical progression (last Tg level 41059 ng/ml in OCT-2022) and persistent vertebral pain. Significant BM progression was documented on 18-F-FDG PET and CT scans, the latter also revealing pulmonary disease progression. Tumor RET status was negative. The initiation of cabozantinib is under consideration.

Discussion: We describe a case of FTC with BM at presentation, with prolonged survival, currently 13 years. Although mostly not curative, a multimodal therapeutic approach should be employed by experienced teams to improve patient´s QOL and survival.