Increased Incidence of Thyroid Cancer Among Breast Cancer Survivors: An Analysis of the SEER 9-Database

Program: Abstracts - Orals, Poster Previews, and Posters
Session: THR 044-059-Thyroid Cancer
Thursday, March 5, 2015: 1:00 PM-3:00 PM
Hall D-F, Thyroid (San Diego Convention Center)

Poster Board THR-049
Jennifer Hong Kuo, MD1, John Chabot, MD1, Mary Beth Terry, MD2 and James A Lee, MD3
1Columbia University Medical Center, New York, NY, 2Mailman School of Public Health, Columbia University, New York, NY, 3Columbia University Medical Center, New York
BACKGROUND: An increased incidence of thyroid cancer among patients with breast cancers has been recognized in single institution studies. We sought to further elucidate the relationship between these two disease processes in a population based setting.

METHODS: A retrospective cohort analysis using the SEER-9 database was conducted on patients with breast and thyroid cancer from 1990-2011. Statistical analyses were performed using SPSS software.

RESULTS: 499,402 patients with breast cancer and 53,853 patients with thyroid cancer were included in the study. Age stratification demonstrated that the incidence of thyroid cancer among breast cancer patients was higher (81.8%) than the general population (54.8%%) in patients ≥ 50 years old. Breast cancer survivors (B1T) developed thyroid cancer at a median of 4.0±0.1 years (SE) after their primary diagnosis. When compared to patients with breast cancer (TC) only, B1T patients were younger (55.0±0.36 vs 61.4±0.02, p<0.0001) with smaller breast cancers (15.0±0.52mm vs. 20.5±0.03mm, p<0.001) and there was no difference in ER/PR positivity or lymph node involvement. However, a greater number of patients did receive adjuvant radiation therapy (48.9% vs 44.0%, p=0.001).

B1T patients developed thyroid cancer at an older age (61.4±0.37 vs 48.3±0.07, p<0.0001) than the general population (TC). These patients have smaller thyroid tumors (11.0 ± 0.6mm vs 14.0 ± 0.10mm, p<0.0001) with less cervical lymph node involvement (2.3±0.03 vs 1.0±0.11,  p<0.0001),  and less radioactive iodine (41.8% vs 46.2$, p=0.003) positivity. B1T patients also have a greater percentage of follicular variant papillary thyroid cancer (31.0% vs 27.8%).

CONCLUSION: Breast cancer survivors are at higher risk for developing thyroid cancer than the general population. Adjuvant radiation therapy is a risk factor for the development of thyroid cancer. These patients have a higher percentage of follicular variant papillary thyroid cancer. Recognition of this association between thyroid and breast cancer should prompt vigilant screening in these cancer patient populations. In addition, further investigation into the relationship of breast and thyroid cancer is warranted.

Nothing to Disclose: JHK, JC, MBT, JAL

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