B. Gui1,2, Y. R. Wuu1,2, S. Kaur1,3, M. Tulchinsky1,2, S. Saha1,2, N. Seetharamu1,4, W. J. Talcott1,5, L. Potters5,6, and M. Ghaly1,2; 1Northwell, Lake Success, NY, 2Department of Radiation Medicine, Northwell, Lake Success, NY, 3Department of Internal Medicine, Northwell, Lake Success, NY, 4Department of MedIcal Oncology, Northwell, Lake Success, NY, 5Department of Radiation Medicine, Northwell, New York, NY, 6Northwell, New Hyde Park, NY
Purpose/Objective(s): Differentiated thyroid cancer (DTC) is usually associated with a good prognosis. While tyrosine kinase inhibitors (TKIs) have shown significant improvement in overall outcomes for patients with iodine-refractory disease, locoregional failure does occur. Locoregional progression can be particularly challenging due to the proximity of the aerodigestive tract and can adversely affect quality of life and survival. Our study aims to assess the efficacy of stereotactic body radiotherapy (SBRT) for locoregional progressive disease in patients with thyroid cancer receiving TKIs. Materials/
Methods: Between August 2016 and November 2023, 19 patients with non-anaplastic thyroid cancer were treated with SBRT and TKIs for locoregional progression. Demographics and treatment-related characteristics were collected. Treatment endpoints including local control (LC), progression-free survival (PFS), overall survival (OS), and toxicities were recorded. Patients with anaplastic histology, incomplete treatment, or without follow-up information were excluded. Results: Of 19 patients meeting the criteria, 11 were female. The mean age of 71 years old. Fourteen lesions were differentiated papillary thyroid cancer, 4 dedifferentiated papillary thyroid, and 2 had other histologies. Eleven patients had disease within the thyroid bed, 5 with postoperative soft tissue neck recurrence, and 4 had cervical nodal metastases. SBRT median dose was 40 Gy (range 35- 50Gy) delivered in five biweekly fractions. Lenvatinib was the TKI in the majority of the cases (n=14), followed by dabrafenib/trametinib (n=4) and cabozantinib (n=2). Planning target volume (PTV) average volume was 175 cc, V95 = 145cc, and D90 = 99%. No grade 3 or 4 toxicities were observed. 5 patients developed grade 2 dysphagia and 4 with fatigue. After a median follow-up of 23 months (range 7-63 months), four patients suffered local progression with an actuarial 12 month LC of 78 % and 24 month LC of 62%. 12 and 24 months PFS and overall survival were 62.8%, 52.3%, 89.2%, and 82.3%, respectively. Conclusion: The use of SBRT in combination with TKIs in iodine-refractory patients appears to be safe and effective for locoregional relapse. Further studies are necessary to define the role of stereotactic body radiotherapy in the management of thyroid cancer.
