Risk Factors for Cardiovascular Disease Among Thyroid Cancer Survivors

Findings From the Utah Cancer Survivors Study

Jihye Park; Brenna E. Blackburn; Patricia A. Ganz; Kerry Rowe; John Snyder; Yuan Wan; Vikrant Deshmukh; Michael Newman; Alison Fraser; Ken Smith; Kim Herget; Anne C. Kirchhoff; Dev Abraham; Jaewhan Kim; Marcus Monroe; Mia Hashibe

Disclosures

J Clin Endocrinol Metab. 2018;103(7):2468-2477. 

In This Article

Abstract and Introduction

Abstract

Context: Thyroid cancer survivors are at high risk of developing multiple cardiac and vascular conditions as consequence of cancer diagnosis and treatment. However, it is still unclear how the baseline and prognostic factors, as well as cancer treatments, play a role in increasing cardiac and vascular disease risk among thyroid cancer survivors.

Objective: To investigate the association between potential risk factors, treatment effects, and cardiovascular disease (CVD) outcomes in thyroid cancer survivors.

Design, Setting, Patients: Primary thyroid cancer survivors, diagnosed from 1997 to 2012 (n = 3822), were identified using the statewide Utah Population Database. The medical records were used to ascertain information on risk factors and CVD outcomes. Cox proportional hazards models were used to assess the risk of CVD with baseline demographic data and clinical factors.

Results: Among thyroid cancer survivors, age and year at cancer diagnosis, cancer stage, sex, baseline body mass index, baseline comorbidities, and TSH suppression therapy were significantly associated with CVD risk 1 to 5 years after cancer diagnosis. Patients who were male, overweight or obese, older at cancer diagnosis, and diagnosed with cancer since 2005 had an increased risk of CVD compared with patients who were female, had a normal body mass index, were younger at cancer diagnosis, and diagnosed with cancer from 1997 to 1999. Administration of TSH suppression therapy, distant metastases at cancer diagnosis, and a higher Charlson comorbidity index score were associated with an increased CVD risk among thyroid cancer survivors.

Conclusions: Our findings suggest that examining the effect of thyroid cancer diagnosis, cancer treatment, and demographic characteristics on the risk of CVD is critical.

Introduction

Thyroid cancer is the eighth most common cancer in the United States, with an estimated 64,300 new cases diagnosed in 2016.[1] In the United States, Utah has the third highest incidence rate of thyroid cancer at 19.03 per 100,000 population.[2] The 5-year survival rate of thyroid cancer was 98.1% from 2006 to 2012.[1] However, with the increasing trend of new cases, thyroid cancer is expected to surpass other cancers and become the fourth most common cancer in the United States by 2030.[3]

The primary treatment of patients with thyroid cancer is surgery, either total or partial thyroidectomy, with most undergoing total thyroidectomy (86%).[4] Among the patients with papillary or follicular thyroid cancer who received surgery, nearly one-half of them additionally receive radioactive iodine (RAI) to treat either residual cancer or ablate the remnant thyroid tissue.[4] Although chemotherapy is rarely prescribed for patients with thyroid cancer, except when metastasis is present, TSH suppression therapy or TSH replacement therapy is often used to further reduce the risk of recurrence in select cases.[4,5]

Given that patients with thyroid cancer are relatively younger at diagnosis with a higher rate of survival, it is important to study the long-term effects of cancer treatment and evaluate the quality of life of thyroid cancer survivors with a near-normal life expectancy.[6–8] According to results from previous studies and guidelines, RAI is associated with an increased risk of cardiovascular diseases (CVDs), and prolonged thyroxine exposure or TSH suppressive therapy increases the risk of large artery impairment and small arterial stiffness (which has been accepted as a CVD surrogate marker), hypertension, cardiac arrhythmias, and cardiovascular-specific mortality.[5,9–18]

Recently, we reported a study, in which we examined the risks of circulatory health conditions after thyroid cancer diagnosis compared with cancer-free individuals.[19] In that study, we found that thyroid cancer survivors have an increased risk of several circulatory conditions compared with the matched cancer-free population, and these were significantly elevated with an older age at cancer diagnosis, male sex, obesity, and higher Charlson comorbidity index (CCI).[19] In an attempt to further address these associations and better understand how the baseline and prognostic factors, as well as cancer treatments, play a role in increasing cardiac and vascular disease risk among thyroid cancer survivors, we assessed the risk factors for CVD among thyroid cancer survivors in the state of Utah.

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