2782 - Patterns of Recurrence and Outcomes in Differentiated Thyroid Carcinoma Patients Treated with External Beam Radiotherapy

10:45am - 12:00pm PT

Hall F

Screen: 33

POSTER

Presenter(s)

Shivanshu Kumar, BS - University of South Florida, Tampa, FL

S. Kumar¹, M. Echevarria², N. Razavian², J. J. Caudell², and G. Q. Yang²; ¹University of South Florida, Tampa, FL, ²H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, FL

Purpose/Objective(s):

External beam radiotherapy for differentiated thyroid carcinomas (DTCs) is typically reserved for patients with high-risk disease including those with tracheal, recurrent laryngeal nerve or esophageal involvement, gross disease after resection, and/or unresectable disease. Herein, we evaluated outcomes and patterns of recurrences for patients with DTC treated with external beam radiation at a tertiary academic center.

Materials/Methods:

After IRB approval, patients with treated with a definitive dose of RT between 2008 and 2023 were identified from an institutional data base. Only patients treated with IMRT technique with the primary intent of locoregional control were included for analysis. Local control (LC), regional control (RC), distant metastases (DM) and overall survival(OS) and analyzed through Kaplan-Meier analysis (KM). Causes of death were individually investigated to determine if locoregional disease was a likely contributor.

Results:

A total of sixty-two patients were identified and included for analysis. Median age was 68 years (range 17-89), with a median follow-up after RT of 37 months. The majority of patients had T4a (59.7%) and/or N1b disease (42.9%); about one-third of patients (32.3%) had known DM at time of treatment. The most common doses and fractionation regimens were 6600 cGy over 30 fractions (n=20), and 6000 cGy in 30 (n=18). In terms of pattern of recurrence, the 3-year LC, RC, and DM rates were 100.0%, 100.0%, and 66.2%, respectively. At 5 years, the rates of LC, RC, and DM were 97.2%, 94.4%, and 61.1%, respectively. Following RT, the 3- and 5-year OS was 72.8% and 51.0%, respectively. Among patients who died (n=26), only 2 (7.6%) were attributable to uncontrolled neck disease; the most common cause of death was uncontrolled metastatic disease (n=10, 38.5%).

Conclusion:

In this cohort of patients with high-risk DTC , RT demonstrated excellent local and regional control, while distant disease was the most common cause of death. As systemic target therapies are increasingly incorporated for patients with locally advanced DTC, RT should be considered to maintain locoregional disease control.