FIRST RESULTS OF RADIOIODINE THERAPY OF MULTIFOCAL AND DISSEMINATED FUNCTIONAL THYROID AUTONOMY USING A TCTUS-ADAPTED DOSE CONCEPT

Aim: The presented study examines prospectively the efficiency of a do se concept for radioiodine therapy (RIT) adapted to the pretherapeutic Tc-99m-pertechnetate thyroid uptake under suppression (TcTUs) in pati ents with multifocal (MFA) and disseminated (DISA) autonomy. This conc ept considers the total thyroid as target Volume and uses target doses from 150 Gy to 300 Gy according to the TcTUs, which is as a measure f or the ''autonomous volume'' of the thyroid. Methods: The data of 75 p atients (54 female, 21 mate; age 71 +/- 9 years) with MFA or DISA were evaluated. RIT was performed on patients presenting with normal Value s for free triiodothyronine and thyroxine and endogenous suppression o f the basal thyrotropin (TSH). The following target doses were used: f or a TcTUs of 1,5-2,5% 150 Gy, for 2,51-3,5% 200 Gy, for 3,51-4,5% 250 Gy, and for >4,5% 300 Gy. The radiation dose to be administered was c alculated using a modified Marinelli formula. The therapy was consider ed as successful when the basal TSH was above 0,5 mU/l and autonomous areas had dissapeared in thyroid scintigraphy or the TcTU was below 1, 5%, respectively. The average follow-up period was 8 +/- 4 months. Res ults: The success rates average to 92%. Only in one case a subsequent subclinical hypothyreoidism and in a further case an immunogenic hyper thyroidism occured. Conclusion: The presented data indicate, that even patients with a marked autonomy (TcTUs >3,5%) can thus expected to be cured by of a onetime therapy with success rate of over 90% using the presented dose concept. The rate of early hypothyroidism can alltoget her be estimated as very tow.