Overwhelming rapid metabolic and structural response to apatinib in radioiodine refractory differentiated thyroid cancer

// Yansong Lin 1, * , Chen Wang 1, * , Wen Gao 2 , Ruixue Cui 1 and Jun Liang 3 1 Department of Nuclear Medicine, Peking Union Medical College Hospital, Beijing 100730, China 2 Department of Oncology, The Affiliated Hospital of Qingdao University, Qingdao 266555, China 3 Department of Oncology, Peking University International Hospital, Beijing 102206, China * These authors have contributed equally to this work Correspondence to: Yansong Lin, email: linys@pumch.cn Jun Liang, email: liangjun1959@aliyun.com Keywords: apatinib, radioiodine refractory differentiated thyroid cancer, thyroglobulin, maximum standard uptake value, safety Received: September 26, 2016     Accepted: January 08, 2017     Published: February 02, 2017 ABSTRACT Currently, patients with radioiodine refractory differentiated thyroid cancer (RAIR-DTC) have limited treatment options. In this study, we aimed to assess the short-term efficacy and safety of apatinib in RAIR-DTC. Ten adult patients were prospectively enrolled to receive oral apatinib (750 mg q.d). The primary endpoints were change in serum thyroglobulin (Tg) concentration, disease control rate (DCR) and objective response rate (ORR) based on RECIST 1.1 criteria. The secondary endpoints included change in glucose metabolism, evaluated by maximum standard uptake value (SUVmax), and safety. As early as 2 weeks after apatinib treatment, the serum Tg concentration decreased by 21.0% in 8 patients available for detection without interference, and a further sharp decline by 81.4% compared with the baseline level occurred at 8 weeks post-treatment. The DCR and ORR were 100% (10/10) and 90% (9/10), respectively. The sum of tumor diameter shrank to 22.8±8.1 mm from 38.8±15.7 mm ( P =0.001). Moreover, a significant decrease in SUVmax was observed from 6.53±5.14 to 2.56±1.67 and 2.45±1.48 at 4-week and 8-week time-points after treatment ( P =0.032 and 0.020), respectively. The common grade 3 adverse events (AEs) included hand-foot-skin reaction (50%), hypertension (30%), and hypocalcemia (20%). No severe AE related to apatinib was observed during treatment. Hence, apatinib seems to be a promising therapeutic option for RAIR-DTC patients. Apart from RECIST 1.1 criteria, the biochemical marker (Tg) and glucose metabolism index (SUVmax) could be adopted in assessing the early response to TKI in RAIR-DTC.