Endocrine Abstracts

Purpose: SPECT/CT has numerous advantages over planar and traditional SPECT images. The aim of this study was to evaluate the role of SPECT/CT after radioiodine treatment of patients with differentiated thyroid cancer (DTC) in early risk classification and in prediction of late prognosis.

Methods: One hundred and eighty-one consecutive patients with DTC were investigated after their first radioiodine treatment. The risk for recurrence based on ATA 2009 classification was low, intermediate and high in 67, 93 and 21 cases, respectively. ETA classification showed low risk in 86, high risk in 95 patients. Planar image from the neck, whole body scan and SPECT/CT from the neck and chest were carried out in all patients 4–6 days after oral administration of 1100–3700 MBq radioiodine.

Results: SPECT/CT was positive in 25.9% of patients, detecting lymph node metastases in 42, lung and bone involvement in 8 and 3 patients, respectively, resulting in the early reclassification of 57 cases (31%). No evidence of disease was found in 140 cases at 9–12 months after radioiodine treatment and 144 patients at the end of follow-up (median 55 months). The sensitivity, specificity and diagnostic accuracy of risk classification systems to predict the persistence or relapse of the tumor at one year were the followings: ATA: 94, 46, 55%; ETA: 88, 57, 63%; SPECT/CT: 76, 85, 83%. The risk for late recurrence was reevaluated based on the 1-year results. The 1-year risk prediction had high diagnostic value at the end of follow-up: sensitivity: 97, specificity: 96, accuracy: 96%.

Conclusions: SPECT/CT after radioiodine treatment is useful in the early classification of patients and influences the therapeutic plan. Risk stratification based on SPECT/CT has lower sensitivity and higher specificity and diagnostic accuracy than ATA and ETA classification. Reevaluation of patients for risk of relapse is required at 1-year follow-up.