Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_40_2540 - Impact of Surgery and External Beam Radiation Therapy on Local Control in the Treatment of Medullary Thyroid Carcinoma

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Impact of Surgery and External Beam Radiation Therapy on Local Control in the Treatment of Medullary Thyroid Carcinoma
A. Groen1, T. Beckham2, T. Links1, E. Sherman3, R. M. Tuttle4, J. Fagin5, A. Shaha4, C. Sabol6, C. J. Tsai2, S. McBride4, H. P. Bijl1, R. J. Wong7, J. Plukker1, and N. Lee2; 1University of Groningen, University Medical Center Groningen, Groningen, Netherlands, 2Memorial Sloan Kettering Cancer Center, Department of Radiation Oncology, New York, NY, 3Memorial Sloan Kettering Cancer Center, Department of Medical Oncology, New York, NY, 4Memorial Sloan Kettering Cancer Center, New York, NY, 5Memorial Kettering Cancer Center, New York, NY, 6Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 7Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY

Purpose/Objective(s): The purpose of this retrospective study was to report the long-term outcomes of local therapy for medullary thyroid cancer (MTC) and potential indications of postoperative radiotherapy (EBRT).

Materials/Methods: Patients with MTC that were treated with EBRT between 1990 and 2016 or surgery alone between 2000 and 2016 at two tertiary referral centers were included (University Medical Center Groningen and Memorial Sloan Kettering Cancer Center). Local progression free survival (LPFS), distant metastasis free survival (DMFS) and overall survival (OS) were evaluated using the Kaplan-Meier method. Chi-square and Cox regression were used to compare the clinicopathology features between the groups and their impact on LPFS.

Results: Of the 302 included patients, 51 were treated with EBRT, 46 of them after surgical resection. 251 patients had surgery alone. The median follow-up was 60 months. For the overall cohort, the 10-year OS and DMFS were 74.8% and 68.1%, respectively. The 10-year LPFS for the overall cohort was 68.4%. There was no significant difference in LPFS in the EBRT group compared to the surgery only group (EBRT 76.7% vs. surgery 67.1%, P=0.389). There was no difference in LPFS in the EBRT group between patients without residual disease, microscopic, macroscopic and inoperable disease (p=0.455). N1 disease (p=0.000), extrathyroidal extension (p=0.000) and positive margins (p=0.001) were associated with a decreased LPFS in the surgery only cohort. The EBRT cohort had higher rates of microscopic disease (37.3% EBRT vs. 14.7% surgery, p=0.000); macroscopic disease (54.9% EBRT vs. 0.4% surgery, p=0.000); N1 disease (92.2% EBRT vs. 47.8% surgery, p=0.000) and extrathyroidal extension (64.7% EBRT vs. 29.9% surgery, p=0.000).

Conclusion: Our EBRT cohort had a similar rate of LPFS despite significantly higher rates of high risk clinicopathologic features for local failure in the EBRT group. EBRT should be considered in patients with residual disease as it may improve local control rates.

Author Disclosure: A. Groen: None. T. Beckham: None. R. Tuttle: None. C. Tsai: None. N. Lee: Consultant; Lily. Advisory Board; Pfizer, Vertex, Merck.

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