Incremental diagnostic value of SPECT/CT to post-radioiodine therapy planar whole-body scan in patients with papillary thyroid cancer

Abstract

Abstract Purpose This study aimed to assess the value of adding single-photon emission computed tomography/computed tomography (SPECT/CT) to whole-body scan (WBS) in patients with papillary thyroid cancer (PTC). Subjects and methods: This study included 265 patients with PTC (aged > 20 years) who underwent WBS and SPECT/CT after radioiodine treatment. Patients were classified into non-metastasis, lymph node (LN) metastasis, and distant metastasis groups based on the diagnosis by the WBS. In addition, results of the WBS were compared with those of SPECT/CT to WBS, and according, the patients were divided into concordant and discordant subgroups. Results The addition of SPECT/CT changed the diagnosis of WBS in 28 (10.6%) of the 265 patients. The results of comparing the clinicopathological features of the subgroups suggested that the tumor size and serum thyroglobulin (TG) level in the discordant subgroup were significantly different from those in the concordant with the increasing trend in the non-metastasis group. In the distant metastasis group, the serum TG level in the discordant subgroup was significantly lower than that in the concordant subgroup, while the clinic-pathological factors were not different in the LN metastasis group. However, for the LN metastasis and distant metastasis groups, SPECT/CT changed the diagnosis of patients by 21.1% and 50.0%, respectively. Conclusion The results of this study suggest that the addition of SPECT/CT to WBS in patients who have PTC, large initial tumors, or high serum TG levels in the non-metastasis group may offer a more accurate diagnosis. Patients diagnosed with distant metastasis by the WBS and had low TG levels require additional SPECT/CT. Thus, SPECT/CT is recommended for patients diagnosed with LN metastasis and distant metastasis by WBS.