Therapeutic radionuclides in nuclear medicine: current and future prospects

Abstract

The potential use of radionuclides in therapy has been recognized for many decades. A number of radionuclides, such as iodine-131 ((131)I), phosphorous-32 ((32)P), strontium-90 ((90)Sr), and yttrium-90 ((90)Y), have been used successfully for the treatment of many benign and malignant disorders. Recently, the rapid growth of this branch of nuclear medicine has been stimulated by the introduction of a number of new radionuclides and radiopharmaceuticals for the treatment of metastatic bone pain and neuroendocrine and other malignant or non-malignant tumours. Today, the field of radionuclide therapy is enjoying an exciting phase and is poised for greater growth and development in the coming years. For example, in Asia, the high prevalence of thyroid and liver diseases has prompted many novel developments and clinical trials using targeted radionuclide therapy. This paper reviews the characteristics and clinical applications of the commonly available therapeutic radionuclides, as well as the problems and issues involved in translating novel radionuclides into clinical therapies.

Keywords: Molecular targeting; Radioimmunotherapy; Targeted radionuclide therapy; Theranostics; Therapeutic radionuclide.

Fig. 1

Serial ^99mTc methylenediphosphonate (^99mTc-MDP) bone scans in a patient with bone metastasis before (a) and at three (b) and six (c) months after combined treatment of ¹⁵³Sm oxabifore and denosumab (reprinted with permission from Rasulova et al. (2013)) (a) Multiple osteoblastic bone lesions were observed before the treatment. (b) The lesions showed a decreasing trend at the three-month follow-up scan. (c) Complete resolution of the osteoblastic lesions was seen at the six-month follow-up scan

Fig. 2

Graphical illustration of the conjugation of a bifunctional chelating agent to a monoclonal antibody (adapted with permission from Milenic et al. (2004)) The chelating agent has two functionalities: one function is to bind the metallic radionuclides, and the other is to bear the reactive functional group (X) which reacts and covalently binds to N-terminal and ε-amines from lysines on the antibody

Fig. 3

Example of theranostics application ⁶⁸Ga somatostatin receptor (SSTR) enables PET/CT imaging to be done for the follow-up and evaluation of molecular response to peptide receptor radionuclide therapy (PRRNT) with ¹⁷⁷Lu-177/⁹⁰Y-labelled somatostatin analogues. Molecular tumour volume (MTV) can be assessed by quantification of the SSTR density in vivo before and after the PRRNT (reprinted with permission from Baum and Kulkarni (2012)). MTI: molecular tumour index; SUV: standardized uptake value

Fig. 4

Various types of nanoparticles that can be radiolabelled for molecular imaging and targeted radionuclide therapy (reprinted with permission from Hong et al. (2009))

Fig. A1

Dr. Kwan-Hoong NG