Radioiodine Dosimetry in Differentiated Thyroid Cancer: Updated Database and Report of National and International Facilities and Practices

1439 Background: The determination of I-131 therapeutic activity to treat differentiated thyroid cancer (DTC) remains controversial, and two general approaches exist: empiric and dosimetric. The dosimetric approach can be employed using different methods and to date there is no publicly available database that provides information on facilities and practitioners that perform dosimetry and the specific methods used to help determine the activity amount of I-131 for therapy. An epidemiological survey was conducted in order to identify and establish a database of facilities in the US and abroad that use dosimetric methods to determine the activity of I-131 for the treatment of DTC, to assess the different dosimetry methods used, to determine the practice patterns of indications for performing dosimetry and/or reasons for not performing dosimetry, to promote quality of care by the appropriate use of dosimetry methods for optimizing I-131 therapy and to promote future research and standardization in this area of clinical practice. The objective of this report is to update the previously presented list of facilities that perform dosimetry in the US and to expand the epidemiological database by including international facilities. Methods: With the initial support of the SNMMI Committee on Radioiodine Theranostics, the Therapy Center of Excellence, and the Quality and Safety Committee of the SNMMI Value Initiative, a multi-phase survey study was initiated. SurveyMonkey was utilized to distribute survey questions and to collect results. The initial weblink was e-mailed to 7,335 SNMMI members in order to establish a preliminary database of facilities that perform dosimetry. While Survey I collected data to compile the list of facilities that use the dosimetric approach rather than empiric, Survey II questioned various practice patterns and indications for dosimetry and the specific dosimetric methods used. Results: A total of 201 responses were received for Survey I, of which 48 facilities in the US and 26 facilities outside US confirmed performing some type of radioiodine dosimetry. Only 28 responses were received for Survey II, of which 24 were US institutions and 4 were institutions outside US. In the US, 63% (15/24) perform full whole-body (WB) dosimetry and 38% (9/24) facilities perform simplified dosimetry. Of these, 5 facilities perform both full WB and simplified dosimetry. Outside US, one facility performs both full WB and lesional dosimetry, one performs both full WB and simplified dosimetry and 2 facilities have reported to perform only simplified dosimetry. The most common method of full WB dosimetry used overall (both in the US and outside US) was Marinelli et al., also known as Benua-Leeper [1]. For simplified dosimetry, the %48 hr WB retention was the most common approach reported, 38% (5/13). Survey responses indicate that dosimetry is most commonly performed based on selected indications and the most common practice/indication is I-131 treatment of known distant metastatic DTC. Conclusions: This epidemiological study updated the previous public database of facilities and practices in the US providing more detail and the inclusion of international facilities performing some type of radioiodine dosimetry for the treatment of DTC. This database is available online through the SNMMI and ThyCa, Inc. websites and may be used by referring physicians that may be interested to direct patients to facilities that perform and use dosimetrically guided activities of I-131 to treat DTC. In addition, the epidemiological data will not only facilitate future selection of sites that may participate in clinical trials to evaluate empiric vs dosimetrically-guided activities of I-131, but will also advance the standardization of dosimetric practices.[1] Benua RS, et al. A method and rationale for treatment of thyroid carcinoma with the largest, safe dose of 131-I. Frontiers in Thyroidology. New York: Plenum Medical; 1986:1317