Different prognostic values of individual hematologic parameters in papillary thyroid cancer due to age-related changes in immunity

Purpose: Several studies have reported the plausible association of neutrophil-to-lymphocyte ratio (NLR) with the prognosis of papillary thyroid cancer (PTC), but the results are inconsistent. In PTC, chronic inflammation is closely related to tumor progression, and the age of the patient has a great influence on prognosis. Therefore, considering the changes in the immune system with aging, we classified the patients according to age and assessed the prognostic value of individual hematologic parameters. Methods: This retrospective analysis included 1,921 patients who underwent thyroidectomy for PTC. Patients were divided into 2 groups based on their age: Y-group (age < 45) and O-group (age >= 45). Blood counts were measured within 14 days before surgery. Results: The Y-group consisted of 914 patients aged < 45 years and the O-group consisted of 932 patients aged >= 45. In both groups, the common prognostic factors related to disease recurrence were only 6 or more metastatic lymph node and grossly extrathyroidal extension, and hematologic parameters were different between the 2 groups. High Platelet-lymphocyte ratio (PLR) in the Y-group and high NLR in the O-group were identified as independent predictors of disease recurrence (NLR: hazard ratio [HR], 3.28; 95% confidence interval [CI], 1.23-8.73; P = 0.018; PLR: HR, 3.08; 95% CI, 1.26-7.52; P = 0.014). Conclusion: The results suggest that changes in immunity with aging may affect prognosis in patients with PTC, and thus hematologic parameters might be employed as prognostic markers depending on the age of the patients.