The Evolving Role of Nuclear Medicine and Molecular Imaging: Theranostics and Personalized Therapeutic Applications

1 During the last decade, there have been excellent and very rapid advances in “Nuclear Medicine and Molecular Imaging” throughout the world. The developments in radiopharmaceuticals induced evolution of nuclear medicine from imaging certain biologic features to targeted drug delivery designed for the specific characteristics of an individual patient’s disease. While the use of therapeutic radioisotopes was an important but minor component of the therapeutic oncology in the past, now with the development of “Theranostic” applications, intelligent options for targeted internal radionuclide treatments became possible in a variety of tumors and Theranostics started to give rise to a paradigm shift in oncology. “Theranostic” concept in nuclear medicine represent both diagnostic and therapeutic function in one drug formulation and while bridging these two goals. The term “Theranostic” is generated from ‘therapy’ and ‘diagnostics/ diagnosis’ (1). Actually Iodine-131 is the oldest and the most common isotope in theranostic applications. In this case, the same radioisotope Iodine-131 serves for both diagnostic and therapeutic purpose on the basis of using the same target, although Iodine-123 which is the pure gamma emitter isotope of Iodine can take part as the diagnostic agent. Theranostic approach also includes the use of different radioistopes but again depending on the principle of using the same target for both diagnosis and therapy Recently, there have been new “theranostics” agents in clinical practice, which are good examples for theranostic approach with two different radioisotopes. For instance, somatostatin receptors on the surface of the neuroendocrine neoplasia have been used as targets for radionuclide imaging and treatment on the basis of “theranostic” approach. PET Imaging with positron emitter Ga-68 labelled peptides which show affinity to somatostatin receptors and treatment with beta emitter Y-90/Lu-177 labelled peptides targeting these receptors gained wide acceptance in the field (2,3).