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Radioisotopes and Their Future in Medicine

Sydney Grosvenor, Maddie Smack, Eva Stamataki

Introduction

Cancer remains a formidable global health challenge, necessitating innovative and effective treatment approaches. Unlike other forms of cancer treatment, radioisotope therapy has emerged as a promising modality for targeting cancer cells while minimizing damage to healthy tissues. Since the 1950’s radioisotope therapy, a branch of nuclear medicine, has gained prominence due to its unique ability to specifically target cancer cells based on their molecular characteristics.

Radioisotopes, or radioactive isotopes, are variants of chemical elements that have an unstable atomic nuclei. These unstable nuclei undergo spontaneous radioactive decay, emitting radiation in the form of alpha particles, beta particles, or gamma rays as they strive to achieve a more stable state. Their unique properties make them valuable tools in various scientific fields. In particular, radioisotopes have come to play a critical role in the field of oncology, revolutionizing cancer treatment. 

 

Key Steps

  1. Unstable Nuclei: An unstable atomic nucleus contains an excess of either protons or neutrons, which makes it energetically unstable. To increase stability, it undergoes a process called radioactive decay.

  2. Radioactive Decay: During radioactive decay, an unstable nucleus takes on a more stable configuration by emitting radiation in the form of particles (alpha or beta) or electromagnetic waves (gamma rays).

    • Alpha Decay:

      1. In alpha decay, an unstable nucleus emits an alpha particle, which consists of two protons and two neutrons. This process reduces the atomic number of the element by 2 and the atomic mass by 4.

    • Beta Decay:

      1. In beta decay, a neutron in the nucleus is converted into a proton, releasing a beta particle (an electron) in the process. This increases the atomic number by 1 while keeping the atomic mass the same.

    • Gamma Decay:

      1. Gamma decay involves the emission of a high-energy gamma ray, which is a form of electromagnetic radiation that does not change the atomic number of the element nor the atomic mass of the isotope.

  3. Harnessing the Radiation:

    • In medical applications, radioisotopes are chosen based on the type of radiation they emit and their suitability for the intended purpose.

      1. Gamma-Emitting Radioisotopes 

        1. Isotopes (i.e. Technetium-99) commonly used in medical imaging. These isotopes emit gamma rays that can be detected by specialized cameras to create images of internal structures in the body.

      2. Beta-emitting isotopes 

        1. Isotopes (i.e. Iodine-131) commonly used in cancer treatment. They release beta particles that can penetrate tissue and damage cancerous cells.

      3. Alpha-emitting isotopes 

        1. Isotopes (i.e. Actinium-225) commonly used in targeted alpha particle therapy. They release high-energy alpha particles, which have a short range and can be directed specifically at cancer cells.

Mechanisms of Radioisotope Therapy

Radioisotope therapy primarily employs two mechanisms to target cancer cells: internal radiation (brachytherapy) and external radiation (external beam radiotherapy). Internal radiation involves the direct injection of radioisotopes into the tumor or the bloodstream, while external radiation uses external sources of radiation. One of the key advantages of radioisotope therapy is its potential for highly targeted treatment. Radiopharmaceuticals, compounds that combine radioisotopes with specific molecules, can selectively accumulate in cancer cells. This allows for precision in delivering radiation, minimizing harm to surrounding healthy tissues.

Internal Radiation

  • Brachytherapy 

    • Brachytherapy involves placing sealed sources of radioisotopes directly into or near the tumor site. This allows for the delivery of high doses of radiation to the cancerous tissue while minimizing exposure to surrounding healthy tissues. Common isotopes used in brachytherapy include Iodine-125 (I-125) and Cesium-131 (Cs-131).

  • Radioimmunotherapy (RIT)

    • Radioimmunotherapy combines the precision of monoclonal antibodies with the destructive power of radioisotopes. In this technique, a radioisotope is attached to a monoclonal antibody specifically designed to target cancer cells. This allows for the selective delivery of radiation to cancerous tissues, minimizing damage to healthy cells. Common radioisotopes used in RIT include Iodine-131 (I-131) and Yttrium-90 (Y-90).

      • Typically, this form of radioimmunotherapy is applied within the body inside the immune system, yet not within the tumor.

External Radiation

  • Targeted Alpha Particle Therapy (TAT)

    • Targeted Alpha Particle Therapy is a cutting-edge approach that utilizes alpha-emitting radioisotopes for cancer treatment. Unlike beta or gamma radiation, alpha particles have high linear energy transfer (LET), which means they deposit their energy over a shorter distance, causing more damage to cancer cells while sparing surrounding healthy tissues. Prominent alpha-emitting radioisotopes in TAT include Actinium-225 (Ac-225) and Bismuth-213 (Bi-213).

 

Advantages of Radioisotope-Based Cancer Treatment

  • Targeted Precision: Radioisotopes allow for precise targeting of cancer cells, minimizing damage to healthy tissues.

  • Short Half-Life: Many therapeutic radioisotopes have short half-lives, reducing the duration of radiation exposure and minimizing long-term side effects.

  • Personalized Medicine: Radioisotope-based therapies can be tailored to individual patients based on the specific characteristics of their tumors.

  • Improved Quality of Life: Radioisotope therapy can lead to enhanced quality of life by reducing symptoms and improving overall well-being.

Disadvantages and Side Effects of Radioisotope-Based Cancer Treatment 

  • Sore ,dry or itchy skin 

  • Tiredness starts during treatment and can continue for several weeks or months after treatment finishes.

  • Hair loss 

  • Problems with eating and drinking 

  • Emotional issues such as stress and anxiety 

  • Radiotherapy can damage your body’s lymphatic system 

  • There is  risk of developing another type of cancer in the years after the treatment 


 

Conclusion

The integration of radioisotopes into cancer treatment represents a significant advancement in oncology. These powerful tools offer targeted and personalized therapies, ushering in a new era of precision medicine. With ongoing research and technological advancements, radioisotope-based treatments continue to evolve, promising even more effective and efficient strategies in the fight against cancer. 

 

Sources

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