WHAT IS Lu PSMA (LUTETIUM-PROSTATE SPECIFIC MEMBRANE ANTIGEN) THERAPY?
Lu177 PSMA Therapy is a treatment for patients with prostate cancer, especially those who have become refractory to conventional therapy. Lutetium PSMA therapy helps to slow down the growth of the cancer cells, reduce the size of the tumours and most importantly improve the quality of life of the patients by reducing the pain caused by the cancer.
WHAT IS PSMA?
Many prostate cancers, in particular those that have spread or become resistant to hormonal therapies, express a unique receptor on their cell surface called Prostate Specific Membrane Antigen (PSMA). When Prostate Cancer metastasizes i.e. spreads to other parts of the body, the PSMA receptor is expressed over the sites of metastases as well.
PSMA is an excellent target for both Radionuclide Imaging & Therapy of Prostate Cancer for several reasons:
- It is expressed in practically all Prostate Cancers in all stages of the disease
- It gets upregulated in hormone refractory or metastatic disease
- It is an integral cell membrane protein and not released into circulation
- The PSMA is internalised after Antibody Binding (Receptor-mediated Endocytosis).
HOW DOES Lu PSMA THERAPY WORK?
Lutetium-177 is a radioactive substance that emits beta radiation, a destructive kind of radiation. Lutetium-177 is bound to a small peptide which attaches to the PSMA receptor expressed on the cancer cell surface. The Lutetium 177 – PSMA complex, thus attached to the prostate cancer cell, then emits killing radiation causing cell death of the cancer cell. Since the penetration of the emitted beta particle is very small, the surrounding normal cells are spared.
HOW IS THE THERAPY DONE?
Lu177 PSMA is administered intravenously. The patient is admitted to the hospital for 24 hours. A kidney function scan called a MAG3/EC scan is done prior to the administration of the Lu177 PSMA. The patient is usually hydrated by intravenous fluids before and after the administration of the Lu177 PSMA over a period of 24 hours.
WHAT ARE THE SIDE EFFECTS OF Lu PSMA THERAPY?
Lu177 PSMA is well tolerated. The most common side effects are a slightly dry mouth, fatigue and nausea. There may also be a slight fall in the white blood cells and platelets about 2 – 3 weeks after the Lu177 PSMA administration. Usually, these side effects are mild and transient and recover spontaneously without any active treatment. The chances of serious or life-threatening complications are extremely rare
WHAT IS THE RESPONSE RATE WITH Lu PSMA THERAPY?
The response rates of Lu177 PSMA depend on the tumour biology of prostate cancer, the initial Gleason Score, the extent of disease and the responses to prior therapies. Typically, more than 70% of patients demonstrate a reduction in S. PSA and a shrinkage of tumours following Lu177 PSMA therapy. Nearly all patients demonstrate a reduction in pain and an improvement in global health by the second dose of therapy.
WHEN WOULD THE DOCTOR CONSIDER USING THIS THERAPY?
Lu PSMA Therapy is a very specific therapy and is used for managing metastatic Prostate Cancer or when Prostate Cancer is no longer responsive to other types of treatment.
The therapy is offered to patients of Advanced Castration-resistant Metastatic Prostate Cancer with evidence of tumour progression are eligible for this therapy. Cancer progression may manifest as :
- Rising Serum PSA levels
- Increase in the size or number of the metastatic lesions on CT/MRI or Ga68 PSMA scans
- Increasing pain or other worsening symptoms due to the disease
Lu177 PSMA Therapy cannot be given to patients in case of
- Severe renal insufficiency
- Severe haematological compromise
WHAT ARE THE TREATMENT SCHEDULES WITH Lu PSMA THERAPY?
Most patients undergo three-four treatment cycles at intervals of 8-12 weeks. The number of cycles and the interim duration may vary between individuals depending on the response and interim assessments. The average dose of Lu PSMA Therapy administered is in the range of 5.5-11GBq per treatment and the doses are based on pre-treatment dosimetry (Dosimetry is the measurement, calculation and assessment of the ionising radiation dose absorbed by the human body).
For treatment, the patient is admitted in the hospital in a Specialised High Dose Radioisotope Therapy Unit for monitoring and radiation protection.
WHY SHOULD I CHOSE THE NUCLEAR MEDICINE THERAPY CENTRE AT FORTIS MEMORIAL & RESEARCH INSTITUTE (FMRI), GURUGRAM (HARYANA, INDIA)?
The Nuclear Medicine Therapy Centre at FMRI was one of the first institutes to offer Radio-ligand Therapy with Lu PSMA, and today, the center receives patients from the country and from across the world. All cases are discussed in a multidisciplinary tumor board and an entire team of specialists from different specialties actually looks after the patient. The patient outcomes of the center are at par with the best centers of the world.