Analysis of common factors influencing the 131I therapeutic efficacy on differentiated thyroid cancer

Objectives The aim is to investigate the risk factors influencing the 131I therapeutic efficacy and prognosis on patients with differentiated thyroid cancer (DTC) by analyzing retrospectively their clinical and pathological features and preoperative thyroid hormone level.

Methods 337 patients with DTC were included. The group was divided into several subgroups according to the preoperational thyroid hormone levels and TNM stages. All data was analyzed based on the stimulating Tg level, TgAb level, and outcome of 131I-WBS in 12 months post treatment with 131I and evaluated the therapeutic efficacy.

Results The therapeutic efficacy was influenced by preoperative free FT3 level, there was significantly better effect in patients with preoperative FT3 level above 3.1 pmol/L than those below the level (P=0.005). Preoperative free FT4 (P=0.069) and TSH levels (P = 0.668) had no effect. Therapeutic efficacy for female patients was significantly superior to male patients (P=0.000). When local soft tissue was involved, therapeutic efficacy was worse (P=0.013).Therapeutic efficacy was significantly better in patients that maximum diameter of tumor was less than 1cm (P=0.000) and 1~2cm (P=0.003) than those tumor diameter was 2~4cm, but there was no statistical difference between less than 1cm and 1~2cm (P=0.323). Therapeutic efficacy in patients without lymph node metastasis was significantly better than those with lymph node metastasis (P=0.000), and was greatly related to the lymph node number (P=0.000). The patients combined with benign thyroid disease had a better therapeutic efficacy than those without any other thyroid disease (P=0.000), and the influence of different types of benign thyroid disease were also quite different (P=0.010).

Conclusions There was a worse iodine-131 therapeutic efficacy for those patients who were men, the preoperative FT3 level less than 3.1pmol / L, local soft tissue involved, tumor size more than 2cm, and lymph node metastasis. The iodine dose should be properly elevated for patients with the above features