Endocrine Abstracts

Background

The 2015 American Thyroid Association (ATA) Risk Stratification System for differentiated thyroid cancer (DTC) is designed to predict response to therapy and recurring disease. Although age is not incorporated as a risk factor, recent research suggests that the addition of age can improve this system. However, these studies comprised low number of patients with ATA High Risk, low numbers of patients with follicular thyroid cancer (FTC), and did not distinguish between papillary thyroid cancer (PTC) and FTC. The aim of our study was therefore to investigate the influence of age on disease outcome in ATA High Risk patients with a focus on differences between patients with PTC and FTC.

Methods

We retrospectively studied adult patients with DTC who were diagnosed and/or treated at a Dutch university hospital between January 2002 and December 2015. All patients fulfilled the 2015 ATA High Risk criteria. Logistic regression and Cox proportional hazards models were used to estimate the effects of age and several age cutoffs (per five years increment between 20 and 80 years) on four disease outcomes: (i) response to therapy, (ii) developing no evidence of disease, (iii) recurrence, and (iv) disease specific survival (DSS).

Results

We included 236 patients with High Risk DTC (32% FTC) with a mean age of 56 years and a median follow-up of 6 years. During follow-up, 14% of the 79 patients that achieved excellent response developed a recurrence. For both PTC and FTC, age had a significant influence on having an excellent response after initial therapy, developing NED, recurrence, and DSS. For FTC, an age cutoff of either 65 years or 70 years seemed to be statically optimal for the different disease outcomes, while this was either 50 years or 60 years for PTC.

Conclusion

In a population of patients with High Risk DTC, age has a significant inverse influence on disease outcomes. Slightly different optimal age cutoffs were identified for the different outcomes, and these cutoffs differed between PTC and FTC. Therefore, age should be considered to be included as a risk factor in the ATA Risk Stratification System, and when doing this, PTC and FTC should be treated as separate entities.