Neutrophil-to-lymphocyte ratio as an independent factor for worse prognosis in radioiodine refractory thyroid cancer patients.

PURPOSE: This study aimed to evaluate neutrophil to lymphocyte ratio (NLR) as a laboratory biomarker in radioactive iodine-refractory (RAIR) locally advanced and/or metastatic differentiated thyroid cancer (DTC) and determine its correlation with overall survival (OS).

METHODS: We retrospectively included 172 patients with locally advanced and/or metastatic RAIR DTC admitted between 1993 and 2021 at INCA. Age at diagnosis, histology, presence of distant metastasis (DM), DM site, neutrophil-to- lymphocyte ratio (NLR), imaging studies such as PET/CT results, progression free survival (PFS) and overall survival (OS) data were analyzed. NLR was calculated at the time of locally advanced and/or metastatic disease diagnosis and the cutoff value was 3. Survival curves were established using the Kaplan-Meier method. The confidence interval is 95%, and a p-value of less than 0.05 was considered statistically significant RESULTS: Out of 172 patients, 106 were locally advanced, and 150 presented DM at some point during follow-up. Regarding NLR data, 35 had NLR over 3 and 137 had NLR under 3. Higher NLR at was associated with shorter OS (6 vs. 10; p = 0.05) and with highest SUV on FDG PET-CT (15.9 vs. 7.7, p = 0.013). We found no association between higher NLR and age at diagnosis, DM or final status.

CONCLUSION: NLR higher than 3 at the time of locally advanced and/or metastatic disease diagnosis is an independent fator for shorter OS in RAIR DTC patients. Noteworthy higher NLR was also associated with highest SUV on FDG PET-CT in this population.