OBJECTIVETo evaluate the response of (131)I therapy and to explore the influencing factors in non-metastatic differentiated thyroid cancer (DTC) patients with preablative stimulated thyroglobulin (ps-Tg) above 10 ng/ml.

METHODSThe study included 157 DTC patients who had undergone total or near total thyroidectomy and subsequent (131)I therapy with ps-Tg>10 ng/ml, and they were divided into 3 groups as excellent response (ER, 49 cases), acceptable response (AR, 36 cases), and incomplete response (IR, 72 cases) according to the response to (131)I therapy. We compared the clinicopathologic features and ps-Tg levels among 3 groups, as well as ps-Tg levels between IR and non-IR groups. The ROC curve was employed to evaluate the predictive value of ps-Tg levels in (131)I therapy responses.

RESULTSThe three groups showed significant difference in ps-Tg levels (H=35.142, P<0.001), gender (χ(2)=6.82, P=0.033), extrathyroid invasion (H=31.380, P<0.001), and lymph metastases (H=14.375, P=0.001). The ps-Tg level in IR is higher than that in non-IR (U=1384.5, P<0.001), while it was not significantly different between ER and AR (U=771.5, P=0.326). The diagnostic critical point (DCP) of ps-Tg to differentiate IR and non-IR was 28.3 ng/ml (sensitivity 57.5%, specificity 87.1%), with a corresponding area under the ROC curve (AUC) of 0.774 (95%CI: 0.701-0.847).

CONCLUSIONSNear-half (45.86%) non-metastatic DTC patients with ps-Tg above 10 ng/ml are more susceptible to IR. The level of ps-Tg>28.3 ng/ml may be a useful and sensitive diagnostic marker for predicting incomplete response.