Nuclear Medicine: The Beauty of Theranostics

Abstract

The field of Nuclear Medicine had witnessed significant advancement in the past two decades, particularly within the area of theranostics. Basically, the term “Theranostics” is a fusion of two words – “Diagnostics” and “Therapeutics”. The backbone concept behind is “we see what we treat, and then we treat what we see”. The principle involves the use of a pharmaceutical ligand, either of the same molecular structure or an analogue, to serve either as a diagnostic or therapeutic agent based on the choice and nature of the labelling radio-isotope. This presentation will mainly cover three cutting-edge and innovative topics within the field of Nuclear Medicine: theranostics for prostatic carcinoma (PCa), neuroendocrine tumor (NET) and hepatocellular carcinoma (HCC). We will explore the basic concept and applications for these diseases by discussing the currently common used radio-isotopes for disease evaluation and therapy. Furthermore, we will discuss how to tailor make the pre-treatment imaging regime in order to personalize the treatment delivery and its potential impact on patient outcome.

Theranostics for Prostatic Carcinoma: We will assess how to utilize the positron emission tomography/computed tomography (PET/CT) imaging with injection of 18F-Prostate Specific Membrane Antigen (PSMA) inhibitor to reveal the PSMA overexpression of PCa. By replacing the radio-isotope with Lutetium-177 (177Lu), the beta emission of 177Lu-PSMA enables the delivery of internal radiation to the pathology while sparing the surrounding normal tissue.

Theranostics for Neuroendocrine Tumor: We will discuss various Gallium-68 (68Ga) labeled DOTA peptides (such as 68Ga-DOTATOC and 68Ga-DOTATATE) as somatostatin analogues to reveal the somatostatin receptor (SSTR) expression of NET. Additionally, we will review the treatment efficacy of 177Lu-DOTATATE in radionuclide therapy.

Theranostics for Hepatocellular Carcinoma: We will explore the application of Technetium-99m labeled Macroaggregated Albumin (99mTc-MAA) as a surrogate radiotracer in SPECT/CT for planning Yttrium-90 (90Y) microsphere radioembolization treatment in HCC patient. Instead of using physical parameters from CT or MRI as part of conventional 90Y-microsphere radioembolization treatment protocol, which is based on a recommended fixed dose of 120Gy, we will delve into the significance of pre-treatment Dual Tracer PET/CT using 11C-Acetate and 18F-Fluorodeoxyglucose, in evaluation of HCC cellular differentiation based on cytokinetic properties and radiosensitivities of HCC, which aids in tailoring the dosage prescription of 90Y-microsphere for individual patient.

Conclusion: The field of Nuclear Medicine has experienced a remarkable blossoming in the area of theranostics. By combing diagnostics and therapeutics into a single modality, it enables more individualized treatment management and provides improved patient outcome. This presentation has provided an overview of the concept and applications of theranostics in Nuclear Medicine with various novel radio-isotopes.