Postablation 131I scintigraphy with neck and thorax SPECT―CT and stimulated serum thyroglobulin level predict the outcome of patients with differentiated thyroid cancer

Objective: Neck and thorax single photon emission computed tomography with computed tomography (SPECT―CT) improves the reliability of postablation 131I whole-body scan (WBS) for differentiated thyroid cancer (DTC). The aim of this study was to assess the prognostic value for persistent or recurrent disease of postablation 131I scintigraphy combining WBS and neck and thorax SPECT―CT with that of the previously known predictive factors. Methods: This is a single referral center prospective study with a median follow-up of 29 months. Postablation 131I WBS and neck and thorax SPECT―CT were performed in 170 consecutive patients treated between 2006 and 2008. Stimulated serum thyroglobulin (Tg) and anti-thyroglobulin antibodies (TgAb) levels were measured. The impact on disease-free survival of age; gender; postablation 131I scintigraphy; stimulated serum Tg level; T. N, and M status: and macroscopic lymph node involvement was assessed by univariate and multivariate analyses. Results: Persistent or recurrent disease was observed in 32 (19%) patients. In the whole group of patients, only positive WBS with SPECT―CT was related to an increased risk of persistent or recurrent disease (hazards ratio (HR)=65.21. 95% confidence interval (CI)=26.03―163.39, P<0.0001). In patients without TgAb (n=146), both positive WBS with SPECT―CT (HR=18.86, 95% CI= 5.02-70.85, P<0.0001) and serum Tg level ≥ 58 ng/ml (HR=4.42, 95% CI=1.18―16.53, P=0.0271) were associated with an increased risk. Conclusion: In patients with DTC, the cross analysis of postablation 131I scintigraphy with neck and thorax SPECT―CT and stimulated serum Tg level enables early assessment of the risk of persistent or recurrent disease.