Survival and Death Causes in Thyroid Cancer in Taiwan: A Nationwide Case-Control Cohort Study

Role of Cancer History in Cardiovascular Mortality Among Different Age-group Patients With Differentiated Thyroid Cancer

Background

Cardiovascular disease (CVD) is the leading cause of noncancer-related mortality among differentiated thyroid cancer (DTC) survivors, which accounts for a large portion of subsequent primary malignancies in childhood cancer survivors. This study aims to assess the risk of cardiovascular mortality among DTC as a second primary malignancy (DTC-2) patients compared with DTC as a first primary malignancy (DTC-1) and the general population.

Methods

Using the Surveillance, Epidemiology, and End Results database, we conducted a population-based cohort study including 159 395 DTC-1 and 20 010 DTC-2 patients diagnosed older than 30 between 1975 and 2020 and the corresponding US population (71 214 642 person-years; 41 420 893 cardiovascular deaths). Compared with general-population and DTC-1 patients, we calculated incidence rate ratios (IRRs) of cardiovascular deaths among DTC-2 patients using Poisson regression. To adjust for unmeasured confounders, we performed a nested, case-crossover analysis among DTC-2 patients who died from CVD.

Results

Although DTC-2 patients had a comparable risk compared with the population (IRR 1.01) and a mildly increased risk of cardiovascular mortality compared with DTC-1 patients (IRR 1.26), the association was pronounced among individuals aged 30 to 74 years, especially 30 to 44 years (DTC-2 vs population: IRR 8.89; DTC-2 vs DTC-1: IRR 3.00). The risk elevation was greatest within the first month after diagnosis, compared with the population. The case-crossover analysis confirmed these results.

Conclusion

DTC-2 patients are at increased risk of cardiovascular mortality. Clinicians should carefully monitor CVD and manage other CVD-related factors, such as exogenous thyroxine and emotional distress, for DTC-2 patients, especially for those under 75 years.

Novelty and Impact Statements

This study is the first comprehensive investigation into the cardiovascular mortality of DTC-2, revealing a higher risk compared to DTC-1 and the general population, especially for cases between 30 and 74 years old. The risk elevation was greatest within the first month after diagnosis. These findings emphasize the restriction of thyroid hormone suppression therapy and reinforce stress management to prevent premature DTC-2 patients from cardiovascular death.

Trends in thyroid cancer burden in Taiwan over two decades

PURPOSE

Thyroid cancer incidence has increased over recent decades with considerable geographic variations in incidence patterns. Here, we analyzed temporal trends in the incidence and mortality rates of thyroid cancer in Taiwan.

METHODS

We obtained age-standardized rates at a national level using data from the Taiwan Cancer Registry annual reports from 1995 to 2019. Trends in age-standardized rates were characterized by joinpoint regression analysis.

RESULTS

The age-standardized incidence rate of thyroid cancer increased from 3.00 per 100,000 person-years in 1995 to 15.46 per 100,000 person-years in 2019 (p < 0.001). Significant upward trends were observed in virtually all age groups, including adolescents and the geriatric population. The average annual percent changes were 7.97%, 2.60%, 2.77%, and 1.43% for papillary, follicular, medullary, and anaplastic thyroid cancers, respectively. The mortality rate from thyroid cancer decreased over time in women but remained stable in men.

CONCLUSION

The incidence rates of thyroid cancer have steadily increased across gender, age groups, and tumor types over the past two decades. Future studies are needed to investigate potential etiological factors other than overdiagnosis that may drive these trends.

Association between thyroid cancer and cardiovascular disease: A meta-analysis

Objective

To determine the association between thyroid cancer and coronary artery disease, atrial fibrillation, cerebrovascular disease, and cardiovascular disease mortality.

Methods

The PubMed, Embase, and Cochrane Library databases were searched for eligible studies from inception to September 22, 2022. Keywords included "thyroid cancer", "atrial fibrillation", "coronary artery disease", "cerebrovascular disease", and "mortality". Primary outcomes included the incidence of coronary artery disease, cerebrovascular disease, atrial fibrillation, and cardiovascular disease mortality among patients with thyroid cancer. Secondary outcomes included cardiovascular disease events among those with thyroid cancer that received or did not receive radioactive iodine or lenvatinib. Estimates were pooled using fixed- and random-effects meta-analysis.

Results

A total of 771,220 patients who underwent thyroidectomy in 15 studies were included. Risk for cerebrovascular disease (risk ratio [RR] 1.15 [95% confidence interval (CI) 1.10-1.21]) and atrial fibrillation [RR 1.59 (95% CI: 1.45-1.73)] were significantly increased. Risk for coronary artery disease was significantly increased [RR 1.12 (95% CI: 1.08-1.17)] in the common effect model. Cardiovascular disease mortality associated with thyroid cancer was not significant [RR 0.93 (95% CI: 0.59-1.45)]. Radioactive iodine had a neutral effect on cardiovascular disease [RR 1.00 (95% CI: 0.87-1.16)], and there was no beneficial nor harmful effect among different RAI doses.

Conclusions

Thyroid cancer was significantly associated with a higher risk for cerebrovascular disease and atrial fibrillation; however, the hazard risk was not different between patients with and without radioactive iodine treatment. Thyroid cancer treatment should be individualized considering the potential harms and benefits to cardiovascular health.

Cause of Death Among Patients With Thyroid Cancer: A Population-Based Study

Background

Over the last decades, the number of patients diagnosed with thyroid carcinoma has been increasing, highlighting the importance of comprehensively evaluating causes of death among these patients. This study aimed to comprehensively characterize the risk of death and causes of death in patients with thyroid carcinoma.

Methods

A total of 183,641 patients diagnosed with an index thyroid tumor were identified from the Surveillance, Epidemiology, and End Result database (1975-2016). Standardized mortality rates (SMRs) for non-cancer deaths were calculated to evaluate mortality risk and to compare mortality risks with the cancer-free US population. Cumulative mortality rates were calculated to explore the factors associated with higher risk of deaths.

Results

There were 22,386 deaths recorded during follow-up, of which only 31.0% were due to thyroid cancer and 46.4% due to non-cancer causes. Non-cancer mortality risk among patients with thyroid cancer was nearly 1.6-fold (SMR=1.59) that of the general population. Cardiovascular diseases were the leading cause of non-cancer deaths, accounting for 21.3% of all deaths in thyroid cancer patients. Non-cancer causes were the dominant cause of death in thyroid cancer survivors as of the third year post-diagnosis. We found that males with thyroid cancer had a higher risk of all-cause mortality compared with females. The risk of suicide was highest in the first post-diagnostic year (<1 year: SMR=1.51). The long-term risk of Alzheimer's disease was notably increased in thyroid cancer patients (>5 years: SMR=8.27).

Conclusion

Non-cancer comorbidities have become the major risks of death in patients with thyroid tumor in the US, as opposed to death from the tumor itself. Clinicians and researchers should be aware of these risk trends in order to conduct timely intervention strategies.