EP18 – A second RAI treatment does not improve disease classification in most DTC patients with biochemical or loco-regional structural incomplete response to initial treatment

      Benbassat, Carlos2,3; Hirsch, Dania1,2; Gorshtein, Alexander1,2; Robenshtok, Eyal1,2; Masri-Iraqi, Hiba1,2; Akirov, Amit1,2; Duskin Bitan, Hadar1,2; Shimon, Ilan1,2 1 Institute of Endocrinology, Rabin Medical Center, Beilinson Hospital, Petach Tikva, Israel  2 Sackler Faculty of Medicine, Tel Aviv University,Tel Aviv, Israel 3 Endocrine Institute, Assaf Harofeh Medical Center, Zerifin, Israel Introduction: The role of repeated RAI treatments for persistent/recurrent loco-regional DTC is unclear. Objective: To investigate the impact of a second RAI treatment (2ndRAI) in patients with incomplete response to initial treatment and no distant metastases. Methods:  Files of patients diagnosed in 1991-2013 who underwent at least two RAI treatments at a single institution were reviewed. Exclusion criteria were receipt of <50 mCi at initial treatment and distant metastases. Stimulated thyroglobulin levels (stTg) and imaging findings were compared before and 1-2 years after the 2ndRAI. Results: The cohort included 166 patients (104 females, age 46.6+17 years). Of the 116 patients who were not re-operated before the 2ndRAI, 53 had positive neck imaging findings. After the 2ndRAI, lesions size decreased in 5, increased in 10 and remained stable in 26.  Mean stTg insignificantly increased after the treatment. In the other 63/116 patients, who had biochemical incomplete response, stTg decreased from 41.9±56 to 24.6±57 ng/ml (p=0.003). In the 50 patients who were re-operated prior to the 2ndRAI, no significant change in stTg was detected and 21 (42%) still had positive imaging findings 1-2 years later. Despite additional treatment in 64/166 patients (38.6%), only 60 patients (36.1%) had no evidence of disease at last follow-up (7.4±5.8 years after 2ndRAI). Conclusions: A second RAI treatment does not improve imaging or biochemical findings in DTC patients showing loco-regional structural incomplete response to initial treatment. It significantly decreases thyroglobulin levels in patients with biochemical incomplete response. Most patients still have evidence of disease after this treatment.


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