Clinical outcome and influencing factors for postoperative papillary thyroid cancer with unexplained elevated Tg prior 131I therapy

Abstract

Abstract Purpose This study aimed to assess the short-term therapeutic response after radioiodine (131I) adjuvant therapy (RAT) and long-term clinical outcome for postoperative papillary thyroid carcinoma (PTC) patients with elevated thyroglobulin (Tg) but no structural disease, and to investigate the related factors affecting the response. Methods From April 2016 to June 2019, 165 postoperative PTC patients with preablative stimulated thyroglobulin (ps-Tg) > 10 ng/ml but no structurally evident disease who undertook RAT in our institutions were retrospectively enrolled. The responses were assessed 6 months post RAT and at the end of follow-up. Univariate and multivariate analyses were used to investigate the effects of 10 observed factors on the long-term therapeutic response. A receiver operating characteristic (ROC) curve was used to determine the cut-off values of Tg to predict incomplete response (IR). Results Six months after RAT, ER, IDR, BIR, SIR were achieved in 13.94%, 29.70%, 30.30%, 26.06% of 165 patients, respectively. With a median follow-up of 58 months, the responses were identified in 33.30%, 21.82%, 15.15%, 29.70%, respectively. The N stage (OR: 3.874, P=0.002) was independent factor associated with SIR and suppressed Tg (sup-Tg) 6 months post RAT (OR: 2.256, P<0.001) was independent factor associated with IR. ROC curve analysis showed that the cutoff value for sup-Tg 6 months post RAT to predict IR was 0.585ng/ml. Conclusion The proportion of patients developing structural disease within 5 years was close to 30% in postoperative PTC patients with unexplained elevated Tg. The N stage and sup-Tg 6 months post RAT were conducive to predict the long-term treatment response of these patients.