MON-418 - A Rare Case of Anaplastic Thyroid Carcinoma with A Survival Exceeding 6 Years

Background: Anaplastic thyroid cancer (ATC) is an extremely aggressive malignancy with a median survival of 4-6 months. Emerging treatment modalities, including antiangiogenic, targeted therapies, and immunotherapy, have improved outcomes in selected patients. Nonetheless, long-term survival beyond 6 years is still exceptionally rare, regardless of treatment modalities.

Case: In April 2019, a 65-year-old male was incidentally found to have a 5.2 x 4.4x 4.8 cm right thyroid nodule on the chest CT for lung cancer screening. The patient denied any compression symptoms, dysphagia and voice changes. Thyroid ultrasound revealed a round, well-defined, mixed echogenic predominantly hypoechoic solid mass with multiple microcalcifications, and mild internal vascularity. Fine needle aspiration showed malignant spindle cells positive for vimentin, negative for PAX8, AE1/3, TTF-1, thyroglobulin and p63, consistent with ATC. PET/CT showed possible spread to cervical lymph nodes (LN) and MRI of entire spine and brain showed no metastasis. The initial treatment plan was extensive tumor debulking followed by chemoradiation. Based on patient preference, he underwent right hemithyroidectomy, isthmusectomy, left subtotal lobectomy, and bilateral neck dissection as debulking surgery in Nov 2019. R recurrent laryngeal nerve was sacrificed, and a total of 89 LNs were resected. Surprisingly, postoperative pathology demonstrated clean surgical margin without any LN involvement, despite focal angioinvasion. The final tumor stage was T3aN0M0. Comprehensive genomic profiling by next-generation sequencing revealed no actionable mutations (including BRAF, MEK, NTRK, RET). Adjuvant chemotherapy with carboplatin/paclitaxel was discontinued after one cycle due to extreme fatigue and the patient did not follow up with oncologist. The patient completed adjuvant radiotherapy (total dose of 6600cGy) to the tumor bed and at-risk lymphatics. There is no evidence of recurrence by follow-up imagings (CT chest, neck and PET/CT). Until the time of this report, which is beyond 6 years after the initial surgery/chemoradiation therapy, the patient has remained asymptomatic and highly functional.

Discussion: This case highlights the possibility of exceptional long-term survival in patients with intrathyroidal ATC without lymph node or distant metastases if diagnosed early. It underscores the survival benefit of complete surgical resection followed by adjuvant radiotherapy, even in the absence of effective systemic therapy. Further studies are needed to better understand prognostic and protective factors associated with prolonged survival in anaplastic thyroid carcinoma.

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