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Men with a history of thyroid cancer had a higher risk of cardiovascular disease (CVD) compared with women, researchers found.

Among a large cohort of thyroid cancer survivors, the risk for developing CVD was significantly higher in men than women (HR 1.46, 95% CI 1.31-1.62), reported Jihye Park, MSPH, of the Huntsman Cancer Institute in Salt Lake City, and colleagues.

Not surprisingly, thyroid cancer survivors who were overweight or obese also had a significantly higher risk for CVD (HR 1.24, 95% CI 1.11-1.39; HR 1.41, 95% CI 1.25-1.60, respectively), the team wrote in the .

"Our findings suggest that thyroid cancer survivors should be continuously monitored and screened for CVD for both earlier detection and better preventative care," recommended the study's senior author, Mia Hashibe, PhD, also of Huntsman, in a statement.

The study also found the following other clinical factors to be associated with an increased risk of CVD among thyroid cancer survivors:

• Any comorbidity versus no comorbidity: HR 4.47 (95% CI 3.87-5.15)
• Distant metastases versus localized cancer: HR 1.35 (95% CI 1.03-1.77)
• Having received thyroid stimulating hormone (TSH) suppression therapy: HR 1.25 (95% CI 1.12-1.40)

Age also seemed to predict future CVD risk, with older thyroid cancer survivors showing a higher associated heart risk compared with patients under age 40 at the time of cancer diagnosis (HR 1.66, 95% CI 1.46-1.88 [age 40-65]; HR 2.84, 95% CI 2.46-3.27 [age >65]).

The analysis included a total of 3,822 patient from the Utah Population Database who had thyroid cancer -- nearly 92% of whom had the papillary carcinoma type. Almost all patients underwent surgical treatment, including thyroidectomy or thyroid lobectomy, while nearly 53% also received adjuvant radioactive iodine (RAI) treatment after surgery.

The development of CVD, which was stratified for 1-5 years, 5-10 years, and over 10 years after cancer diagnosis, was defined as heart disease; hypertension; cerebrovascular disease; disease of the arteries, arterioles, and capillaries; and disease of the veins and lymphatics. Nearly half of the patients had at least one heart or vascular-related disease within the first 1-5 years after thyroid cancer diagnosis.

Within that first 1-5 years after cancer diagnosis, significantly more cancer survivors with CVD died compared with those who did not develop CVD (11.4% versus 2.7%, P<0.001).

Although there were no notable differences in regards to cancer characteristics between patients who developed CVD and those who did not, more patients who received a cancer diagnosis in 2005-2009 (HR 1.42, 95% CI 1.19-1.69) and 2010-2012 (HR 1.26, 95% CI 1.05-1.51) developed CVD compared with those diagnosed in 1997-1999.

"One possible explanation for these associations may be the increasing proportion of patients who undergo TSH suppression and radiation therapy over the years due to changes in treatment strategies," the researchers hypothesized, adding that future studies should investigate clinical practice changes and the possible impact on long-term cardiac and circulatory conditions in thyroid cancer patients.

Regarding the type of cancer treatment, the group found a marginal association between the risk of cerebrovascular disease with receiving RAI treatment as opposed to those who underwent surgical treatment only (HR 1.44, 95% CI 0.99-2.09).

"This association is biologically plausible as carotid arteries are located immediately adjacent to the thyroid gland and carotid artery intimal thickening has been reported following RAI for benign disease."

In terms of study limitations, Park et al said that since information about dose was not available, it was not possible to evaluate dose-dependent relationships. In addition, the most common dosage of RAI during the time of the study ranged from 30 mCi for remnant ablation and 100-150 mCi for therapeutic ablation for locoregional and extensive disease.

"For a better quality of life among thyroid cancer survivors, future research is needed to demonstrate the long-term health effects after cancer diagnosis, not only to provide individualized clinical intervention but also to prevent the risk of fatal conditions as well," the researchers concluded.

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