Radionuclide/Radioligand Therapy | Xofigo and Pluvicto
Radioligand therapy (RLT), also known as radionuclide therapy, marks a significant advancement in precision oncology, offering a targeted approach to cancer treatment. This innovative therapy uses molecules labeled with radioactive isotopes (radioligands) that specifically bind to cancer cells, delivering localized radiation directly to the tumor or metastatic sites. RLT combines the specificity of molecular targeting agents (i.e. monoclonal antibodies that bind specifically with certain cancer cells) with the therapeutic efficacy of radiation, making it a potent option for managing certain types of cancers. By leveraging advanced imaging platforms, RLT provides accurate delivery of therapeutic doses, minimizing impact on healthy tissues. The most common forms of radionuclide or radioligand therapy include Xofigo, Pluvicto (both for prostate cancer) and Zevalin (for lymphomas).
What is Xofigo (Radium-223) for Prostate Cancer?
Xofigo (Radium-223 dichloride) represents a pioneering radiopharmaceutical used in the treatment of metastatic hormone-resistant prostate cancer (mCRPC) with bone metastases. Xofigo is an isotope of radium, which molecularly mimics calcium. In areas of the bone affected by prostate cancer, the body wants to repair itself, drawing on any nearby calcium molecules to do so – and if a radium-223 molecule is there, it will, like a “Trojan horse”, go into the bone where the cancer cells are and while it is there, will deliver a very potent form of radiation known as an alpha-particle. This form of radiation induces double-stranded DNA breaks in cancer cells, leading to their destruction. Xofigo’s targeted mechanism of action allows for the treatment of bone metastases with minimal effects on surrounding healthy bone marrow, offering a valuable option for patients with advanced prostate cancer.
What is Pluvicto (Lutetium-177 PSMA-617) for Prostate Cancer?
Pluvicto (Lutetium-177 PSMA-617) is a novel radioligand therapeutic approved for the treatment of PSMA-positive metastatic hormone resistant prostate cancer (mCRPC). Unlike Xofigo which only goes to bone, Pluvicto is an antibody molecule that binds to the Prostate-Specific Membrane Antigen (PSMA) protein which is expressed on prostate cancer cells. The Pluvicto molecule ligand is “tagged” with the radioactive isotope Lutetium-177, and when the ligand binds to the PSMA receptor on the cancer cell, it can deliver a targeted radiation to that site, both at the primary tumor and metastatic sites, providing a systemic yet focused treatment approach. Pluvicto has demonstrated significant efficacy in reducing tumor size and progression, improving survival rates in patients with advanced prostate cancer.
What is Zevalin (Ibritumomab Tiuxetan) for Lymphoma?
Zevalin (Ibritumomab Tiuxetan) is a targeted radiopharmaceutical therapy used in the treatment of certain types of non-Hodgkin lymphoma (NHL), specifically focusing on the CD20 antigen expressed on the surface of B-cells. Zevalin is a monoclonal antibody conjugated to the radioactive isotope Yttrium-90, allowing it to deliver targeted radiation directly to the lymphoma cells. This “Trojan horse” approach brings the radiation close to the cancer cells while sparing surrounding healthy tissues. This treatment is particularly beneficial for patients with relapsed or refractory follicular lymphoma, offering a promising option for those who have limited responses to conventional therapies. Zevalin has been shown to effectively reduce tumor burden and prolong progression-free survival, making it a valuable component of lymphoma management strategies.
Who Is a Candidate for Radioligand Therapy?
Candidates for RLT are typically patients with advanced or metastatic cancer that expresses specific targets for the radioligands, such as bone metastases in prostate cancer for Xofigo or PSMA-positive cells for Pluvicto. Ideal candidates are those who have not responded adequately to conventional treatments or for whom other therapies are not suitable. During your consultation with your radiation oncologist, the criteria for treatments will be discussed, along with all expected risks and benefits.
The Process/Procedure
RLT is administered intravenously, with the procedure varying slightly depending on the specific radiopharmaceutical used. Prior to administration, patients undergo thorough evaluation, sometimes to confirm the presence of targetable cancer cells (like a PSMA scan in the case of Pluvicto or a PET scan in the case of Zevalin). The treatment itself is usually outpatient, with the number of sessions dependent on the individual’s response and specific treatment plan. Certain radiation safety protocols may be used after your discharge depending on the type of radiation used in the specific RLT.
Follow-Up After Radioligand Therapy
Follow-up care is crucial after RLT to monitor the effectiveness of the treatment and manage any potential side effects. This typically includes regular imaging studies, blood tests, and clinical assessments. Patients may also receive support for symptom management and overall health maintenance. The follow-up schedule and care plan are personalized, reflecting the patient’s unique treatment response and health status. Often, patients may be candidates for other companion treatments including external beam radiation.
