Abstract B24: A rationale for screening for thyroid malignancy in breast cancer patients
Authors: Stack Brendan C. , Oudin Edouard M. 
Published: September 2020

Introduction: An increased incidence of thyroid cancer in breast cancer patients has been demonstrated in the literature. A recent meta-analysis reports odds ratio of developing thyroid cancer after breast cancer to be 1.55 (Nielsen et al., 2016). The USPSTF and ATA recommend against routine thyroid screening for non-high-risk asymptomatic adults. We aim to obtain demographics of breast cancer patients who develop thyroid cancer and assess their malignancies. We use this assessment to discuss the potential impact that routine thyroid screening could have on breast cancer patients.

Methods: We performed a literature review using PubMed and Web of Science databases and reviewed abstracts of 352 publications. Papers were excluded for nonrelevance or lack of patient-level data. Relevant papers were fully reviewed and their data were compared to population-level data from the SEER database. We then gathered data on breast cancer patients at our home institution who later developed thyroid cancer. Chart review was performed on medical records with relevant diagnostic codes. Exclusions were made for nonrelevance or lack of information. Patient demographics and breast and thyroid cancer characteristics were obtained.

Results: In literature review four papers were used to obtain breast cancer characteristics on 206 patients. Mean age of breast cancer diagnosis (47.07 years) was younger than peak incidence age range for breast cancer reported by SEER registry (75-79 years). There were more patients with ductal carcinoma in situ or infiltrating ductal carcinoma compared to SEER population (97.09% vs. 74.33). Estrogen receptor status was positive less often compared to SEER population (73.23% vs. 80.77). Five papers were used to obtain thyroid cancer characteristics on 230 patients. Mean tumor size was smaller compared to the SEER population (1.017 cm vs. 1.782). There was a higher percentage of nodal involvement (25.90% vs. 19.62) and extrathyroid extension (34.98% vs. 15.37) compared to SEER population. Initial search for home institution breast cancer patients later developing thyroid cancer yielded 108 patients. 39 were included in our study. The majority developed papillary thyroid cancer with a mean tumor size of 0.99 cm. 74.4% were treated with total thyroidectomy.

Conclusion: Screening for thyroid malignancy is a contentious topic. Speculation of the impact thyroid cancer screening could have for breast cancer patients has prompted us to identify the characteristics of these patients and their cancers. Literature review suggests that these patients may develop thyroid cancers with increased lymphovascular involvement and increased extrathyroid extension. If true, it may be worth considering a change in thyroid cancer screening guidelines for female breast cancer patients. Current work is focused on developing more definitive conclusions. We are performing a more in-depth chart review and developing a data collaboration via the Southeastern SHRINE research network to gather more data.

Citation Format: Brendan C. Stack, Edouard M. Oudin. A rationale for screening for thyroid malignancy in breast cancer patients [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr B24.