Thyroid cancer incidence has been steadily increasing over the past few decades in the United States, and it is projected to be one of the leading cancer sites in women in the near future. Papillary thyroid carcinoma accounts for approximately 85% of all thyroid cancers. Some studies report that the increased thyroid cancer incidence is primarily attributed to the incidental and early detection of small, papillary thyroid carcinomas through increased use of high-quality diagnostic imaging techniques; however, this only partially explains the increased incidence. Besides radiation, a well-established risk factor for thyroid cancer, environmental exposures have become an increasing concern as potential risk factors.
Because not all reported findings can be readily explained by incidental and early detection alone — including an increase in environmental exposure-associated gene mutations and geographical differences in thyroid cancer incidence that are likely exposure-associated— investigators at the Icahn School of Medicine at Mount Sinai are interested in exploring the role of environmental exposures in the worldwide thyroid cancer burden.
Increased Thyroid Cancer in Heavily Exposed Populations
An indication that environmental exposures are potentially associated with increased thyroid cancer risk is the reported excess risk of thyroid cancer in heavily exposed populations.
The explosion and collapse of the World Trade Center (WTC) on 9/11 resulted in an aerosol plume exposing residents, commuters, and rescue and recovery workers during and in the months following the disaster. The dust and smoke contained multiple carcinogenic contaminants, such as asbestos, benzene, and dioxins, as well as other pollutants. Follow-up of different WTC-dust exposed cohorts showed an excess thyroid cancer risk with an approximate twofold increase in thyroid cancer incidence rate, compared to the general population.
Another heavily exposed cohort consists of United States Vietnam-era veterans who were exposed to Agent Orange, the most commonly used defoliant during the Vietnam War. Agent Orange was contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD is highly toxic and also chemically stable; therefore, persisting in the environment. Hence, increased thyroid cancer risk has been reported among Vietnam-era veterans.
These examples highlight the importance to investigate the potential link between environmental exposures and thyroid cancer.
Environmental Exposure to Endocrine Disrupting Chemicals
Endocrine disrupting chemical (EDC) are substances or mixtures that alter the function of the endocrine system, including the thyroid gland, leading to adverse health effects. Currently known EDCs include various pesticides, flame retardants, polychlorinated biphenyls (PCBs), phthalates, perfluoroalkyl substances (PFAS), and Biphenyl A (BPA). Exposure to certain EDCs has been associated with thyroid dysfunction and various types of cancer.
Although current literature suggests that exposure to certain flame retardants, PCBs, phthalates, and pesticides may potentially be associated with an increased risk of thyroid cancer, there is an urgent need to investigate the role of EDC exposure in the worldwide thyroid cancer burden to increase the knowledge on the potential hazards of certain chemicals, shape regulatory actions and policies, and ultimately improve population health.
Investigating the Role of Environmental Exposures via Thyroid Research Database
With the creation of Mount Sinai’s Thyroid Research Database, we aim to elucidate the potential role of environmental exposures in thyroid cancer and thyroid disease. The Thyroid Research Database, integrated within the Head and Neck Cancer Research Program, consists of patients who received surgical treatment for a malignant or benign thyroid problem at The Mount Sinai Hospital. Within the database, extensive information will be collected on:
- Clinical characteristics
- Reported past exposures
- Disease management
- Follow-up care
Investigators plan to prospectively enroll patients in order to collect more in-depth information on past exposures using an extensive questionnaire as well as blood collection to monitor exposures at diagnosis and following treatment at regular intervals.
The Role of “Omics” Techniques
To increase our knowledge about the impact of exposures on thyroid carcinogenesis, as well as identifying new potential biomarkers of disease, recent and ongoing advances in the “omics” field will play an essential role. The “omics” field includes a variety of techniques, such as genomics, transcriptomics, proteomics, and metabolomics, which we will use to investigate collected blood and thyroid cancer pathology samples.
Using “omics” techniques, we also plan to investigate thyroid cancer within existing cohorts, such as the previously described WTC cohort and Vietnam Era Veterans cohorts, as well as other cohorts through collaborations with other researchers.
Through the integration of the Thyroid Cancer Research Database, collaborations within and outside The Mount Sinai Hospital, and the use of various research techniques, we will be able to link certain exposures to thyroid carcinogenesis, cancer recurrence or progression, which is invaluable information to improve patient care.