Potential of Technetium and Rhenium Theranostics

While theranostics has transformed the precision medicine landscape over the last decade, there is scope for the development of true theranostic pairs, e.g. diagnostic and therapeutic partners in which any physical, chemical, and biological differences are negligible to in vivo application. Although simple to state in theory, there are, in fact, limited options exhibiting optimal physical characteristics and wholly shared elements. Further compounding real-world application of the traditional theranostic method are additional barriers. The use of PET/CT as the cornerstone of the diagnostic pair in theranostics creates inequity of access and opportunity based on socioeconomic and geographic factors, and the growing demand for both ⁶⁸Ga and ¹⁷⁷Lu is straining production capabilities globally. Improving access to theranostics globally will require novel thinking and infrastructure investment to ensure that patients of all economic and social backgrounds have access to this transformative technology. An approach which is underdeveloped, but which may address gaps in health inequities and improve outcomes, is the application of the widely available generator-produced ^99mTc for imaging and ¹⁸⁸Re for therapy. Despite favourable and near identical radiochemistry, the search for the next generation of theranostic radionuclide pairs seldom references technetium or rhenium radionuclides. Advances in SPECT/CT instrumentation and radiochemistry provide an opportunity to deliver theranostics to communities not serviced by PET-based theranostics. The ¹⁸⁸Re and ^99mTc supply by daily elution of a generator affords significant convenience, flexibility and delayed biomolecule imaging. Low abundance gamma emissions of ¹⁸⁸Re allow serial imaging and dosimetry calculations. ^99mTc / ¹⁸⁸Re theranostics could address inequity in access and opportunity to cutting edge theranostics.