Abstract #1400018: Genetic Alterations in NRAS, TERT, PIK3CA and SPEN Genes Leading to an Aggressive Metastatic RAI Refractory Follicular Thyroid Cancer

Abstract

Follicular thyroid cancer (FTC) is a well-differentiated thyroid tumor and the second most common type after papillary thyroid cancer (PTC) with higher incidence of distant metastases, more aggressive behavior, and poorer outcome than PTC Patient is 43-year-old female with 6.2 cm TR4 left thyroid nodule on Neck US. On Exam, Cricoid is deviated to the right with left thyroid firm nodule. FNA showed Follicular neoplasm. TSH level was 1.59 (0.45-4.70 mIU/L) and Free T4 level: 1.19 (0.78-2.20 ng/dl) CT scan of neck with contrast and MRI thoracic spine: Large, solid heterogenous mass in left thyroid lobe causing lateral displacement and mild narrowing of the trachea with retrosternal extension, Osteolytic lesion of T4 vertebral body and right sided pleura-based mass at the level of T7-T8 with No enlarged cervical lymph nodes. IR biopsy of vertebra: thyroid Origin Metastatic Carcinoma, Patient underwent total thyroidectomy with central neck dissection. Follicular thyroid cancer (STAGE II pT3A,pN1B,pM1) Mutational Testing: Negative BRAF and KRAS with Positive NRAS, PIK3CA, SPEN and TERT. Patient started on TSH suppression therapy. 1 month Later: Thyroglobulin: 2443.4 ng/ml (1.3-31.8), Thyroglobulin Ab< 0.9 (0.0-4.0 IU/ml), TSH 0.02 with Free T4 2.53 FDG PET: Multifocal osseous metastatic disease, predominantly in the axial skeleton Thyrogen stimulated WBS I-123 showed No evidence of residual or metastatic disease. Patient recieved 214 mCi of iodine-131. Post treatment MN scan showed accumulation of iodine in the metastatic bone lesions with small focal activity in the thyroidectomy bed. Post RAI treatment: TG trended to 1102.7 then 1307 Patient Completed 10 fractions of external beam radiation on T4 spine Ultrasound thyroid: No residual thyroid tissue or suspicious lymph nodes Oncology started Bone directed therapy with zoledronate with consideration of PIK3CA mutation targeted therapy with Everolimus or Temsirolimus FTC is more aggressive with poorer prognosis than PTC that is more likely to hematogenously disseminate, with mortality rate of 50%. The neoplastic proliferation of thyroid follicular cells develops by altering multiple molecular pathways such as the PI3K/AKT pathway involving the RAS, RAF, RET, and NTRK1 genes. RAS is a dual activator of the mitogen activated protein kinase and PI3K/AKT pathways TERT is a catalytic subunit of the telomerase complex. Reported in 11–17% of FTC. TERT promoter mutations associated with tumor aggressiveness and mortality PIK3CA encodes p110-alpha, is a catalytic subunit of phosphatidylinositol 3-kinase (PI3K) involves in thyroid cancer tumorigenesis and progression, reported in 7.7% of FTC with sensitivity to therapies targeting PI3K49-56, AKT57-58, or mTOR59-66. In our patient, pretreatment MN scan failed to show RAI avid lesions but PET showed increase FDG uptake and since receiving RAI treatment helped in lowering TG that indicate a possibility of mixture of RAI avid and non-RAI avid lesions existing at same time so RAI treatment is still recommended despite negative Diagnostic Scan for persistent elevated TG.