Main Session
Sep
29
PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care
3516 - External Beam Radiotherapy is Effective and Well Tolerated in Unresectable Primary or Recurrent Differentiated Thyroid Cancer
Presenter(s)
Jana Kobeissi, MD - Cleveland Clinic Foundation, Cleveland, OH
J. M. Kobeissi1, E. E. Obi1, N. M. Woody1, K. Scharf2, R. W. Davis1, Q. Liu3, S. Parikh4, D. S. Buchberger1, D. M. Routman3, N. P. Joshi2, and M. C. Ward5; 1Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH, 2Rush University Medical Center, Chicago, IL, 3Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 4Wake Forest University School of Medicine, Charlotte, NC, 5Atrium Health Levine Cancer, Wake Forest School of Medicine, and Southeast Radiation Oncology Group, Charlotte, NC
Purpose/Objective(s):
While surgery remains the most common tool for locoregional control in differentiated thyroid cancer, some patients are inoperable or have unresectable disease, and limited data exist on the effectiveness of external beam radiation therapy (EBRT) in the modern era. We report a multi-institutional study examining the efficacy of EBRT in treating gross thyroid disease.Materials/Methods:
An IRB-approved, multi-institutional retrospective review was conducted. Patients with differentiated thyroid cancer were included, with a focus on those treated with radiation therapy where gross disease was present in both the upfront and salvage settings. Overall survival and locoregional control were analyzed using the Kaplan-Meier method with Cox proportional hazards analysis to assess the impact of patient, disease, and treatment factors on outcomes.Results:
Thirty-four patients were included, of whom 18 (53%) were female, with a median age of 72 years (range 40-95 years) and a median follow up of 35.2 months. Most were Caucasian non- or former smokers. Five patients were upfront unresectable and were treated with RT definitively, while the remainder had either residual disease after initial resection or at the time of recurrence (N=29, 85%). The initial clinical stage of disease was III-IV in 20 patients with aggressive histology in 20. Among the 29 patients who had upfront surgery, disease was pT4 in 17 and pN1b in 11, with positive margins in 20 and extrathyroidal extension in 21. Sites of gross disease at the time of RT included thyroid bed (N=15), unilateral neck (N=14), bilateral neck (N=3), central neck (N=9), upper mediastinum (N=9), and unresected/residual thyroid gland tissue (N=5). All patients received at least 1 radioactive iodine (RAI) course pre-RT (range 1-4). Median RT dose was 66 Gy (range 40 – 72 Gy) delivered in 32 fractions (range 5-35) to the gross target volume, with 22 plans (65%) also covering elective regions to a median dose of 56.1 Gy (range 36 – 63 Gy). Post-RT, 5 patients received adjuvant RAI, 1 required a feeding tube, and 4 required hospitalizations within 30 days (all unrelated to RT). Median overall survival was 39.5 months (95% CI: 28.6 m – NR). Only 6 patients had locoregional failures, and median locoregional recurrence was not reached. Actuarial 3-year locoregional control was 77.5%. On Cox proportional hazards analysis, RT at the time of recurrence, prior RAI, presence of gross disease in the central neck, and aggressive histology were not significantly predictive of locoregional control or overall survival.Conclusion:
For patients with unresectable or gross residual differentiated thyroid cancer, EBRT can provide excellent locoregional control with limited toxicity and represents a viable salvage option that may delay the need for additional therapy.