Patient age at diagnosis and biological sex in association with postoperative outcomes of thyroidectomy for low-risk papillary thyroid cancer in the U.S. Military Health System

Background: In the United States (U.S.) population, thyroid cancer incidence, aggressiveness, and survival have been shown to vary by patient age at diagnosis and biological sex. Surgery is a primary treatment for low-risk thyroid cancer and surgical outcomes can greatly influence patient outcomes and survival. It is unknown whether patients differ in postoperative outcomes of thyroid cancer surgery by age at diagnosis and sex. We aimed to study the topic in the U.S. Military Health System (MHS) to address this gap in knowledge. Methods: We used the Military Cancer Epidemiology (MilCanEpi) database to study a cohort of patients aged 18 years and older diagnosed with T1-2N0M0 papillary thyroid cancer between 2001 and 2014 who received thyroidectomy surgery. We estimated the adjusted risk ratio (ARR) and 95% confidence intervals (CIs) in association with patient age at diagnosis and biological sex for 30-day general and local thyroid complications and hospital readmissions using multivariable Poisson regression. Results: The study included 2,041 patients with 2.3% experiencing a general complication, 12.1% a thyroid complication, and 13.9% a readmission within 30 days after surgery. Overall, rates of general and thyroid complications as a whole were not statistically different for patients aged 40–49 or 50 years and older relative to age 18–39 years in multivariable models. However, patients 50 years or older had a statistically lower risk of hypoparathyroidism (ARR =0.37; 95% CI: 0.19–0.73) and also lower rates of readmission (ARR =0.68; 95% CI: 0.49–0.93) compared to patients aged 18–39 years. There were no statistically significant differences in the outcomes for men compared to women. Conclusions: In the MHS, we observed some variation in risk of complications and readmissions by patient age at diagnosis for those undergoing thyroidectomy for T1-2N0M0 papillary thyroid cancer. More research is needed to understand the factors underlying lower risk of complications among older adults, or conversely, higher risk for complications among young adult patients with papillary thyroid cancer.