Targeted radionuclide therapy was first used to treat cancer for an ‘over-active’ thyroid using radioactive iodine-131 seeds.
Human Body Imaging
Targeted Alpha Therapy (TAT) has become a promising approach in cancer treatment. As a form of radionuclide therapy, TAT employs alpha-emitting isotopes to selectively target and destroy cancer cells while minimising damage to healthy tissue. In addition, the unique characteristics of alpha particles, such as their high linear energy transfer (LET) and limited penetration range, make TAT an attractive option for patients with metastatic or treatment-resistant cancers. This article will explore the fundamentals of TAT, its advantages, and potential future developments in the field.
Mechanism of Targeted Alpha Therapy
TAT involves using a vector molecule, typically an antibody or a peptide, which specifically binds to an antigen at the surface of cancer cells. This vector molecule is conjugated with an alpha-emitting isotope, such as Actinium-225 (²²⁵Ac) or Radium-223 (²²³Ra), creating a targeted radiopharmaceutical. Upon administration, the radiopharmaceutical accumulates in the tumour tissue due to the high specificity of the vector-antigen interaction, delivering a potent cytotoxic effect to the cancer cells.
Alpha particles, emitted during the radionuclide decay, have a high LET, resulting in dense ionisation and severe DNA damage within a short range of a few cell diameters. This high-energy deposition leads to the death of cancer cells through mechanisms such as DNA double-strand breaks and the generation of reactive oxygen species. On the other hand, the limited penetration range of alpha particles reduces the risk of damage to surrounding healthy tissues, improving the therapeutic index and reducing side effects.
Advantages of Targeted Alpha Therapy
TAT offers several advantages over traditional cancer therapies, such as chemotherapy and external beam radiation therapy. Firstly, the targeted nature of TAT allows for the precise delivery of alpha particles to cancer cells, minimising off-target effects and reducing the risk of damage to healthy tissue. This translates to fewer side effects and improved patient quality of life during treatment.
Secondly, the high potency of alpha particles can overcome resistance to conventional treatments. The short range and high LET of alpha particles enable TAT to effectively destroy cancer cells with hypoxic or radiation-resistant characteristics, often associated with treatment failure and recurrence.
TAT is a promising option for disseminated, metastatic, or micrometastatic disease patients. This is because radiopharmaceuticals can reach cancer cells throughout the body. In addition, this provides a potential treatment option for patients who are not candidates for operation or have cancer cells that are not easily accessible by external radiation.
Future Developments and Conclusion
Research into TAT is ongoing, with numerous clinical trials investigating its efficacy and safety in various cancer types. As our understanding of TAT improves, advancements in vector molecule design and isotope production may further enhance this treatment modality’s therapeutic efficacy and safety profile. Combining TAT with other cancer treatments, such as immunotherapy or targeted therapies, could lead to synergistic effects and improved patient outcomes.
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Targeted radionuclide therapy was first used to treat cancer for an ‘over-active’ thyroid using radioactive iodine-131 seeds.