[Results of TcTUs-optimized radioiodine therapy in multifocal and disseminated autonomy]

The presented study prospectively evaluates the efficacy of optimized radioiodine therapy in patients (pts) with multifocal (MFA) and disseminated (DISA) autonomy. The target dose was related to the total thyroid volume and was increased in moderate and nonlinear increments from 150 to 300 Gy dependent on the pretherapeutic Tc-99m pertechnetate thyroid uptake under suppression (TcTUs). Patients with focal autonomy were treated with a target dose independent of TcTUs and were used as control group.

The data of 641 pts (518 women, 123 men) were evaluated, 466 pts with MFA or DISA and 175 pts with focal autonomy. In pts with MFA and DISA the target dose was increased in four steps: TcTUs < 3%: 150 Gy, > 3-6%: 200 Gy, > 6-12%: 250 Gy and > 12%: 300 Gy. In pts with focal autonomy a fixed target dose of 300 or 400 Gy was applied. The radioactivity to be administered was calculated using a modified Marinelli formula. The follow-up examination was performed at the earliest after four, on average after eight months. Normalization of TSH was the only criterion for successful therapy.

The success rate in pts with latent or manifest hyperthyroidism in focal autonomy was 91.5%, therapy was not successful in 5.1% and hypothyroidism occurred in 3.4%. The average success rate in pts with MFA and DISA was 91.5%, therapy failed in 7.5% and a very low rate of 1% with hypothyroidism was seen.

The presented optimized therapy concept with calculated, nonlinear increase of the target dose according to the TcTUs-level guaranteed even in MFA and DISA a high success rate comparable to that in focal autonomy along with a very low rate of hypothyroidism.