Thyroidectomy tied to CV complications after cancer diagnosis
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Adults with differentiated thyroid cancer who undergo thyroidectomy are at increased risks for atrial fibrillation, cardiovascular disease, increased heart rate and left ventricular mass development, data from a review show.
“Once differentiated thyroid cancer is diagnosed, the patient undergoes thyroidectomy, followed by thyroid-stimulating hormone suppression therapy and/or radioactive iodine therapy, depending on the risk stratification,” Eun-Kyung Lee, MD, PhD, specialist in the division of endocrinology and metabolism at the National Cancer Center Korea, and colleagues wrote in the study background. “TSH suppression by exogenous thyroid hormone replacement is widely recommended to prevent cancer recurrence in patients with high-risk differentiated thyroid cancer, despite the risk of TSH suppression on CVD. An increased risk of atrial fibrillation in patients with differentiated thyroid cancer was suggested by a recently published meta-analysis. However, the risk of thyroid hormone supplementation in patients with differentiated thyroid cancer for CVD other than atrial fibrillation has not been established yet.”
In a meta-analysis, researchers analyzed data from 18 observational studies assessing associations between differentiated thyroid cancer (DTC) and CV outcomes, excluding those that evaluated CVD as a comorbidity before any DTC diagnosis and those that used active surveillance without thyroidectomy or TSH suppression therapy as an intervention (193,320 cases and 225,575 healthy controls). Risk estimates were pooled using random- and fixed-effects models when three or more studies reported on the outcome of interest. Echocardiographic and hemodynamic parameters were examined.
Researchers found that thyroidectomy after DTC was associated with an increased risk for atrial fibrillation, with a pooled RR of 1.55 (95% CI, 1.3-1.84), coronary artery disease (RR = 1.1; 95% CI, 1-1.21), cerebrovascular accidents (RR = 1.15; 95% CI, 1.09-1.2), and all-cause mortality (RR = 1.95; 95% CI, 1.03-3.69).
Thyroidectomy after DTC was also associated with higher diastolic blood pressure, with a standardized mean difference (SMD) of 0.22 (95% CI, 0.01-0.42), heart rate (SMD = 0.37; 95 CI, 0.17-0.57), left ventricular mass index (SMD = 0.66; 95% CI, 0.45-0.88), interventricular septal thickness (SMD = 0.91; 95% CI, 0.33-1.49) and lower early to late ventricular filling velocities (SMD = –0.42; 95 CI, –0.79 to –0.05). Thyroidectomy after DTC was not associated with ejection fraction.
“In this study, patients with DTC had a higher risk of developing atrial fibrillation than the general population and a faster heart rate, consistent with the previous studies,” the researchers wrote. “Interestingly, there was also an increased risk of CAD and cerebrovascular accidents in patients with DTC. However, hypothyroidism is also a risk factor for CAD or cerebrovascular accidents due to atherosclerosis. One possible explanation is the imbalance between thyroxine ... and triiodothyronine ... due to altered deiodinase activity in athyreotic patients.”
The researchers cautioned that the data were retrospective; prospective studies with long-term follow-up are needed to assess CV outcomes and mortality rates.
Perspective
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Maria Papaleontiou, MD
This systematic review and meta-analysis of 18 studies found that patients with differentiated thyroid cancer are at increased risk for cardiovascular disease, including atrial fibrillation and stroke, and worse heart-related parameters, such as increased heart rate, compared with the general population. Even though the discrete underlying mechanisms behind these associations are not entirely clear, these findings highlight that TSH suppression in patients with differentiated thyroid cancer following surgery may play a significant role.
Despite the excellent survival rates for most patients with differentiated thyroid cancer, results from this study have clear implications for clinical practice, as they outline significant CV risks thyroid cancer survivors may face long term. It is therefore vital to optimize thyroid cancer management to individual patients by always balancing potential harms and benefits of treatments. Finally, even though this meta-analysis sheds light on an important topic, large prospective studies with long follow-up are needed to validate these findings and better delineate the effect of thyroid cancer diagnosis and treatments on CV risk.
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