External Beam Radiation Is Not Associated with Improved Survival in Patients with Locally Advanced Medullary Thyroid Cancer

Program: Abstracts - Orals, Poster Previews, and Posters
Session: SAT 270-310-Thyroid Neoplasia (posters)
Saturday, April 2, 2016: 1:15 PM-3:15 PM
Exhibit/Poster Hall (BCEC)

Poster Board SAT 307
Linda Youngwirth*1, Mohamed Adam1, Randall Scheri1 and Sanziana A Roman2
1Duke University Medical Center, 2Duke University Medical Center, Durham, NC
Background: Although the American Thyroid Association recommends external beam radiation for patients with medullary thyroid cancer at high risk for local recurrence, data on this topic remain limited. The purpose of this study was to evaluate the impact of external beam radiation on survival in patients with locally advanced medullary thyroid cancer.

Methods: The National Cancer Database (1998-2012) was queried for all adult patients with medullary thyroid cancer. Inclusion was limited to locally advanced tumors (T3 tumors <4cm and T4 tumors) and patients without distant metastases. The cohort was divided in two groups based on the receipt of external beam radiation. Patient demographic, clinical and pathologic factors at the time of diagnosis were determined for all patients. A binary logistic regression model was developed to determine factors associated with receipt of external beam radiation. A Cox proportional hazards model was used to determine factors associated with survival.

Results: In total, 575 patients met inclusion criteria; 34.3% of patients received external beam radiation. When compared to patients who did not received external beam radiation, those who did were more likely to be male (61.4% vs 48.2%), receive treatment at comprehensive or community facilities (56.3% vs 39.0%), and have larger tumors (4.2 cm vs 3.0 cm) (all p<0.01). Unadjusted overall survival was similar at five years for both groups (65.8% for patients who received external beam radiation and 73.7% for patients who did not; p=0.17).  After adjustment, male gender (OR=1.70, p=0.01), comprehensive facility type (OR=2.05, p<0.01), community facility type (OR=4.05, p<0.01), increasing tumor size (OR=1.01, p=0.04), and regional lymph node metastases (OR=1.90, p=0.03) were associated with receipt of external beam radiation. After adjustment, external beam radiation was not associated with improved survival (HR=1.16, p=0.49).

Conclusion: External beam radiation is not associated with improved survival in patients with locally advanced medullary thyroid cancer. Further studies are needed to determine the potential role for radiation in maintaining local control of disease and quality of life in this challenging patient population.

Nothing to Disclose: LY, MA, RS, SAR

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