Usefulness of albumin-globulin ratio as a clinical prognostic factor in patients with thyroid cancer treated with radioiodine.

Albumin–globulin ratio (AGR), which is calculated by dividing serum albumin by serum globulin, is considered as a cancer-related inflammation biomarker. Although the prognosis of many solid cancers has been shown to be associated with AGR, there are no studies to demonstrate the association between the prognosis of thyroid cancer and AGR. The purpose of this study is to reveal the relationship between AGR and overall survival (OS) in patients with thyroid cancer who received radioactive iodine therapy (RIT). Eighty-eight patients with thyroid cancer who had received RIT for the first time in our institution were included. The values before RIT were adopted as initial measurements for serum albumin, globulin, and thyroglobulin (Tg) and used for analysis. Patients were divided into two groups based on the AGR value. We analyzed the relationship between clinical factors and treatment outcome. The median follow-up period was 92.4 months (range: 30.1–173.9 months). The 5-year OS and progression-free survival (PFS) were 94% and 54%, respectively. Seventeen patients (< 65 years, 8; and ≥ 65 years, 9) died during the follow-up period. Low AGR was significantly associated with OS in both univariate and multivariate analyses (p = 0.0059 and p = 0.0120, respectively). As the 5-year OS was as high as 94%, there was no significant difference in survival rate between the two groups during the first 5 years. However, there seemed to be a remarkable difference in 10 years after the first RIT. On the other hand, Tg was significantly associated with PFS in both univariate and multivariate analyses (p = 0.0016 and p = 0.0441, respectively). In patients under the age of 65, the PFS rate was significantly lower in the low AGR group (p < 0.0001), while there was no difference in PFS rate between the two AGR groups in patients aged 65 years or older. AGR may be used as a prognostic factor in relatively younger patients with thyroid cancer treated with radioiodine, while it may be less useful in the older. Overall, it may be an independent prognostic factor for long-term survival in those with thyroid cancer.