3610 - Effectiveness and Tolerance of Post-Operative External Beam Radiation in Advanced Differentiated Thyroid Cancer
Presenter(s)
K. Scharf1, J. M. Kobeissi2, E. E. Obi3, Q. Liu4, S. Parikh5, R. W. Davis2, N. P. Joshi1, D. S. Buchberger6, M. C. Ward7, D. M. Routman4, and N. M. Woody2; 1Rush University Medical Center, Chicago, IL, 2Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH, 3Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic Foundation, Cleveland, OH, 4Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 5Wake Forest University School of Medicine, Charlotte, NC, 6Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH, 7Atrium Health Levine Cancer, Wake Forest School of Medicine, and Southeast Radiation Oncology Group, Charlotte, NC
Purpose/Objective(s): The role of post-operative radiation therapy (PORT) in the absence of gross disease advanced differentiated thyroid cancer (DTC) remains controversial. Given the lack of prospective data, we evaluated oncologic outcomes and predictors of recurrence and survival for patients receiving PORT for advanced DTC in a multi-institutional cohort.
Materials/Methods: We retrospectively analyzed patients with advanced DTC treated with PORT from a multi-institutional dataset to assess the effect of PORT on the patient, disease, and outcomes. All patients had no gross residual disease at PORT initiation. Overall survival and locoregional control rates were calculated using the Kaplan-Meier method with predictors of outcomes were evaluated using Cox proportional hazards.
Results:
82 patients (Male: n=38, 46%; Female: n=44, 54%) were included in this study. Median age was 65 years (range 27-91 years) and patients were generally medically fit with median KPS 90 (range 60-100) for a median follow up of 46 months (range 0-179). Indications for RT included positive surgical margins (n=29), aggressive histology (n=48), and locoregional recurrence (n=22). Median radiation dose was 62.5 Gy (range 35 Gy to 72 Gy). Twelve percent presented with de novo metastatic disease, and the majority of patients had advanced T-stage at diagnosis. Poorly differentiated histology was present in 11%. Approximately half demonstrated aggressive variants (tall cell, columnar, or other high-risk histologies) prior to PORT. Fifty percent of patients had at least one salvage surgery of whom 20 [24%] had 2 or more surgeries prior to RT. Fifty-five percent of patients had RAI prior to radiation, of whom 12 [15%] had more than one course. Locoregional control (LRC) was 91% at 3 years and 85% at 4 years. Median overall survival was 74 months (range 2.5-113 months). There was no statistically significant association between aggressive histology, prior RAI, or RT at recurrence for locoregional control or overall survival. Prior to RT, seven patients already required laryngectomy, tracheostomy, or feeding tube. Following RT, 4 required tracheostomy or feeding tube.Conclusion: In a cohort of patients with advanced DTC, PORT was well tolerated with modest toxicity and achieved excellent locoregional control and overall survival even in the setting of significant pretreatment. These findings support a clear clinical benefit of adjuvant RT in appropriately selected high-risk patients.