Correlation of recurrence of Graves disease with thyroid gland mass, 24 h radioiodine uptake and the administered therapeutic activity

Full text of publication follows. Aim: in our department, calculation of radioiodine activity to treat patients with Graves Disease (GD) is based on thyroid mass and on the 24 h radioiodine uptake (24h-RIU). The aim of this study was to evaluate the importance of those parameters and of the administered activity in the outcome of radioiodine therapy in patients with GD, considering the need for an additional ¹³¹I treatment. Material and methods: clinical charts of 251 GD patients (202 females, 49 males, mean age 47± 15.3 yr) treated with radioiodine between January 2003 and February 2011 were reviewed. From those, 42 patients relapsed and needed additional ¹³¹I therapy (Group A = 34 females, 8 males; mean age 49.5 ± 16.2 yr). The average time between first treatment and recurrence was 15.9 ± 11.9 months. To obtain a case-control group (Group B), 42 patients successfully submitted to a single course of ¹³¹I therapy, were randomly selected between 2003 and 2007 (33 females, 9 males; mean age 47.3± 15.5 yr). Success of ¹³¹I therapy was defined as an euthyroid or hypothyroid status at 3 years post-therapy without the need for additional radioiodine treatment, surgery or antithyroid medication. Each group was characterized for thyroid mass, 24h-RIU, and radioiodine therapeutic activity administered. A non parametric Mann-Whitney U test has been used for comparison of those parameters between the two groups. Results: Four Group A, the mean (and range) of 24h-RIU, thyroid mass, and therapeutic activity administered were, respectively: 59.1% ± 10.7 (36-82); 78.2 g ± 35.5 (28-172) and 414.4 MBq ± 170.2 (111-814). For Group B were: 53.6% ± 10.9 (32-75); 48 g ± 25.7 (20-170); 362.6 MBq ± 114.7(196.1-740). Statistical analysis showed that the need for a second treatment in GD patients was significantly correlated with thyroid mass (p<0.01) and to 24h-RIU (p<0.033) but not with the administered activity (p>0.05). Conclusions: In our experience, recurrence of Graves Disease after radioiodine therapy is associated with heavy thyroid glands and high values of 24h-radioiodine uptake and but not with the administered therapeutic activity. (authors)