Is ¹³¹I treatment necessary for postoperative DTC patients classified as intermediate- or high-risk with negative...

Several studies have indicated that postoperative differentiated thyroid cancer (DTC) patients with stimulated thyroglobulin (sTg) levels <1 ng/mL could directly transition to thyroid stimulating hormone (TSH) suppression therapy. However, a number of cases with negative sTg have also shown residual thyroid tissue (RTT) or metastases through various imaging examinations. This study aimed to assess the necessity of ¹³¹I treatment for DTC patients classified as intermediate- or high-risk for recurrence with sTg levels below 1 ng/mL.

A retrospective analysis was conducted on a total of 158 postoperative DTC patients classified as intermediate- or high-risk for recurrence with pre-ablation sTg levels below 1 ng/mL, as well as a subgroup of 51 DTC patients with pre-ablation sTg levels below 0.04 ng/mL. A comprehensive comparison was conducted between the results of pre-ablation imaging examinations and post therapy ¹³¹I whole body scans (RxWBS, with SPECT/CT) in terms of RTT, cervical lymph nodes, or distant metastases. The therapeutic response of ¹³¹I treatment was also evaluated.

The presences of RTT or unsuspected metastases were detected in 141 patients by RxWBS: 87.3 % (138/158) exhibited RTT, whereas 16.5 % (26/158) had metastatic lymph nodes. Compare to other pre-ablation imaging modalities, RxWBS demonstrated superior sensitivity in identifying both RTT (87.3 % vs. 37.3 %) and metastatic lymph nodes (16.5 % vs. 2.5 %). Among the 141 patients (89.2 %, 141/158) who were positive on RxWBS, 132 patients (93.6 %, 132/141) achieved an excellent response (ER) after the ¹³¹I treatment.

For postoperative DTC patients classified as intermediate or high risk for recurrence with negative sTg, RTT or metastases may still be present in most cases. ¹³¹I treatment is necessary for these patients regardless of serum sTg results, and a majority of them could have favorable therapeutic response.