Analysis of correlation factors influencing the outcome of initial 131I remnant ablative therapy in intermediate- to high-risk patients with papillary thyroid microcarcinoma.

OBJECTIVE

To investigate the factors influencing the outcome of initial 131I remnant ablative therapy in intermediate- to high-risk patients with papillary thyroid microcarcinoma (PTMC).

METHODS

We divided 99 patients with PTMC who underwent total thyroidectomy into two groups according to their response to initial 131I remnant ablative therapy: excellent response (ER) and non-ER groups. Clinical and laboratory characteristics were collected and retrospectively analyzed using univariate and multivariate binary logistic regression. Receiver operator characteristic (ROC) curves and diagnostic cutoff values were analyzed to evaluate the predictive value of significant quantitative influencing factors for 131I treatment outcomes. A prognostic nomogram model based on the above independent risk factors was established.

RESULTS

Of the 99 eligible patients who accepted the initial 131I treatment following total thyroidectomy, 76 (76.7%) were classified into the ER group and 23 (23.3%) into the non-ER group. The univariate and multivariate analyses showed that extrathyroidal extension [ETE; odds ratio (OR) = 4.769; P = 0.041], preablative thyrotropin (TSH; OR = 0.972; P = 0.017), and stimulated thyroglobulin (sTg; OR = 1.614; P = 0.040) were independent predictors for the therapeutic effect of 131I treatment. Patients with higher sTg (>1.37 ng/ml) and lower TSH (<67.97 mU/l) and ETE tended to have a poor response to initial 131I treatment. The quantification of the therapeutic effect of initial 131I therapy in patients with PTMC using our newly constructed nomogram showed that ETE, preablative sTg, and TSH were contributors to non-ER.

CONCLUSION

Intermediate- to high-risk patients with PTMC after total thyroidectomy who had low pretreatment sTg and high preablative TSH levels and negative ETE were more likely to achieve satisfactory response to initial 131I remnant ablative therapy. Our prognostic nomogram is a valuable tool to enable patients and clinical professionals to be better informed about patients' therapeutic response to initial 131I remnant ablative therapy.