The value of SPECTCT restage in differentiated thyroid cancer (DTC) patients post radioiodine therapy.

Objectives Radioiodine therapy is an essential choice for higher risk patients with DTC post total thyroidectomy. Routinely, whole body scintigraphy (WBS) and SPECTCT imaging techniques are necessary for post radioiodine therapy, especially restage.

Methods During 2012, Jan to 2013, Feb, fifty five patients with moderate to high risk DTC are included. The characteristic of patients are: sex ratio (F/M: 9/2), average and range age (49.7 ; 16-76 year-old). The fifty three cases are papillary thyroid carcinoma and the other two are follicular carcinoma. Twelve patients with lateral compartment lymph nodal metastasis and one with bone metastasis are noted at initial diagnosis. Under withdrawal or rh TSH preparation, empirical administration of radioiodine as 50 to 200 mCi based on personal tailing. All patients received dual WBS and SPECTCT imaging (Philips, Brightviews XCT) at the 5^th and 8^th day post radioiodine therapy.

Results Fifty four patients (98%) with residually functional remnants are detectable, most localization in the pyramid and tubercle. One patient is diagnosed as incidental pyramidal tumor by mean of post radioiodine therapy SPECTCT. There two patients are demonstrated nerve invasion (T4a), but similar stage after SPECTCT diagnosis. However, FDG PETCT demonstrates one recurrence during one year period. Nine patients (16%) have upstage as N1b (six cases) and incidentally single site M1 (two lung and one bone metastasis). For whom with lateral lymph nodal metastasis and bone metastasis (24%) at initial diagnosis, radioiodine WBS and SPECTCT still play a role to elucidate the risk of patients and tail personal follow-up protocol.

Conclusions Post radioiodine therapy WBS and SPECTCT are essentially routine imaging protocol to restage of DTC patients. For known risk DTC patients, SPECTCT is also helpful to tail personal follow-up protocol.