Jimenez LGA, et al. - In patients with low-risk differentiated thyroid cancer (LRDTC), experts assessed the response rate when using a low dose of ­131-I GBq, as well as the impact of clinical and analytical variables on the prediction of complete response. A low dose of 131-I was enough in the majority of patients with LRDTC to reach a complete response at 6-12 months follow-up. A relation of tumor size and pAntiTgAb variables to therapeutic response was noted.

Methods

• Authors conducted a multicenter longitudinal study with patients who were operated on for LRDTC and who had radioiodine remnant ablation with a low-dose of 131-I.
• They evaluated all the patients at 6-12 months and their status was classified as complete (excellent response) or incomplete response (structural incomplete, biochemical incomplete or indeterminate response).
• They analyzed various factors including age, gender, histology, tumor focality and size, stage, time from surgery to treatment, type of thyroid-stimulating hormone (TSH) stimulation, preablation serum thyroglobulin (pTg), antiTg antibodies (pAntiTgAb) and TSH (pTSH) levels in relation to complete response rate.

Results

• As per data, out of 108 patients, 79.6% achieved complete response and the remaining demonstrated incomplete response (2.9, 5.5 and 12% due to biochemical incomplete, structural incomplete and indeterminate response respectively).
• A new dose of 131-I was received by 6 patients.
• Results demonstrated that tumor size and pAntiTgAb were the only factors related to therapeutic response (p=0.03 and p < 0.01, respectively).
• Nonetheless, the only independent factor related to complete ­response was pAntiTgAb .
• Lower pTg was demonstrated by patients with complete response than those with incomplete response (5.1 ± 12.9 vs. 11.2 ± 25 ng/mL) although without statistical significance (p= 0.14).
• Experts did not note any significant difference in the response rate, depending on the thyrotropin stimulation methods.