Radionuclide Therapies: Overview, Types, Procedure & Benefits

Radionuclide Therapies also known as targeted radioisotope therapies are a specialized form of nuclear medicine used to treat various diseases, primarily cancers and thyroid disorders. Unlike traditional external beam radiation, Radionuclide Therapies deliver radiation internally by administering a radioactive substance that seeks out and destroys diseased cells while sparing most healthy tissue. This precision makes these therapies highly effective and often better tolerated than other treatments.

The idea of using radioactive substances to treat disease dates back many decades, with radioactive iodine therapy for thyroid conditions being one of the earliest and most successful examples. Since then, advances in nuclear medicine have led to more sophisticated radionuclide treatments that target a wider range of conditions, especially certain cancers that do not respond well to conventional therapies.

What Are Radionuclide Therapies?

Radionuclide Therapies involve the administration of a radioactive isotope that binds to specific cells in the body. These isotopes emit radiation, damaging the DNA of target cells and stopping their growth or killing them outright. Because the radiation is delivered directly to the diseased cells, side effects to healthy tissues are minimized. Radionuclide treatments can be given orally (as a capsule or liquid), through injection into the bloodstream, or directly into body cavities, depending on the condition being treated.

How Do Radionuclide Therapies Work?

The key to Radionuclide Therapies is the ability to target specific tissues. A radioactive isotope is linked to a molecule often a peptide or antibody that binds to receptors found mainly on the diseased cells. For example, in prostate cancer, Prostate-Specific Membrane Antigen (PSMA) receptors are targeted by radiolabeled molecules that deliver radiation directly to cancerous prostate tissue. In thyroid cancer or hyperthyroidism, radioactive iodine (I-131) is used because thyroid cells naturally absorb iodine, ensuring the radiation is focused where it’s needed most.

Conditions Treated with Radionuclide Therapies

While these therapies were once limited mainly to thyroid diseases, their use has expanded dramatically in recent years. Common uses include:

• Thyroid conditions: Radioactive iodine (I-131) therapy for hyperthyroidism and thyroid cancer.
• Prostate cancer: PSMA-targeted therapies like Lutetium-177 PSMA.
• Neuroendocrine tumors (NETs): Peptide Receptor Radionuclide Therapy (PRRT) with Lutetium-177 DOTATATE.
• Bone metastases: Strontium-89 or Radium-223 to relieve pain and control spread.
• Liver cancer: Selective Internal Radiation Therapy (SIRT) using Yttrium-90 microspheres.

Types of Radionuclide Therapies

Radionuclide Therapies can be categorized by the type of isotope used and the disease being targeted:

1. Radioactive Iodine Therapy (RAI or I-131)

• Primarily used for hyperthyroidism and differentiated thyroid cancer.
• The patient swallows a capsule or liquid containing I-131.
• The thyroid absorbs the iodine, concentrating the radiation where it’s needed.

2. Peptide Receptor Radionuclide Therapy (PRRT)

• Treats neuroendocrine tumors (NETs) using radiolabeled peptides.
• A common example is Lutetium-177 DOTATATE, which binds to somatostatin receptors on tumor cells.
• The patient receives an IV infusion; the radiation damages tumor cells over time.

3. PSMA Therapy

• Used for advanced prostate cancer.
• Radioligands such as Lutetium-177 PSMA bind specifically to PSMA receptors found on prostate cancer cells.
• The therapy is usually given intravenously and may require multiple cycles.

4. Radionuclide Therapy for Bone Pain

• Used to relieve pain from bone metastases, common in advanced prostate or breast cancer.
• Isotopes like Strontium-89 or Radium-223 target areas of increased bone turnover, delivering localized radiation.

5. Selective Internal Radiation Therapy (SIRT)

• Mostly for liver tumors.
• Tiny radioactive beads (Yttrium-90) are injected directly into the liver’s blood supply, delivering radiation precisely to tumors.

Procedure of Radionuclide Therapy

The general steps involved in Radionuclide Therapy include:

1. Consultation and Evaluation

Your doctor will evaluate your medical history, current condition, and previous treatments. Imaging tests such as PET CT, MRI, or SPECT scans may be performed to determine the extent of the disease.

2. Preparation

• Depending on the therapy, you may need to follow a special diet or stop certain medications.
• Thyroid patients may need to follow a low-iodine diet to increase the treatment’s effectiveness.

3. Administration

• The radioactive drug is given by mouth, IV injection, or direct placement in the body.
• The treatment is usually done in a specialized, shielded room to limit exposure to others.
• The patient may stay in the hospital for a few hours to a few days, depending on the isotope used.

4. Post-Treatment Care

• Patients may be advised to limit close contact with others for a period to avoid exposing them to residual radiation.
• Follow-up scans are done to assess how well the therapy worked.
• Additional treatments may be scheduled if needed.

Benefits of Radionuclide Therapies

Radionuclide Therapies offer many advantages over traditional treatments:

• Targeted action: Delivers radiation directly to cancer or diseased cells.
• Minimized side effects: Healthy tissues receive less radiation.
• Effective for hard-to-treat cancers: Especially helpful for tumors that have spread or cannot be removed by surgery.
• Non-invasive: Usually done without major surgery.
• Can be combined with other therapies: Works well alongside chemotherapy, surgery, or external radiation.

Possible Side Effects

Though generally well-tolerated, side effects can occur:

• Fatigue and mild nausea.
• Temporary drop in blood counts.
• Dry mouth (in radioactive iodine therapy).
• Rarely, damage to nearby organs if the radiation spreads.
• Short-term isolation requirements to protect others from exposure.

Tests Used to Plan and Monitor Radionuclide Therapies

Accurate planning and monitoring are vital to success. Common tests include:

• PET CT Scan: Locates active cancer cells and measures treatment effectiveness.
• SPECT Scan: Shows how the radioactive drug is taken up by tissues.
• CT or MRI: Provides structural images to complement functional scans.
• Blood tests: Monitor thyroid function, kidney health, and blood cell counts.
• Biopsy: In some cases, to confirm diagnosis or measure receptor levels.

Conclusion

Radionuclide Therapies have transformed cancer care and treatment for thyroid and neuroendocrine conditions. They offer a precise, patient-friendly option for diseases that are difficult to treat with conventional surgery or radiation. Advances in targeted radioisotopes are expanding the use of these therapies, giving hope to patients with complex or advanced cancers.

Frequently Asked Questions (FAQs)

1. What is Radionuclide Therapy used for?

It is mainly used to treat cancers like thyroid cancer, neuroendocrine tumors, advanced prostate cancer, and bone metastases.

2. How is Radionuclide Therapy different from traditional radiation therapy?

Traditional radiation comes from an external machine, while Radionuclide Therapy delivers radiation from inside the body, directly targeting diseased cells.

3. Is Radionuclide Therapy painful?

No, the procedure itself is painless, though you may feel slight discomfort during injection or minor side effects afterward.

4. How long does Radionuclide Therapy take?

The administration may take an hour or two, but preparation and post-care may extend your visit to a few hours or days, depending on the isotope.

5. Can I be around family after Radionuclide Therapy?

You may need to follow safety instructions to limit radiation exposure to others for a few days.

6. Are there any long-term side effects?

Most side effects are mild and short-term, but your doctor will monitor you for any late effects, especially if repeat treatments are needed.

7. Can Radionuclide Therapy cure cancer?

It may not cure advanced cancers but can significantly shrink tumors, control spread, and relieve symptoms.