WHAT IS LEAD(PB212) PRRT THERAPY & HOW LEAD(PB212) PRRT IS BETTER THAN ACTINIUM(AC225) PRRT THERAPY?
Pb212 has the unique property that it decays first by beta emission into a daughter nuclide called Bi212. Bi212 then decays by alpha emission. So Pb 212 delivers the benefits of both beta and alpha-emitting radionuclides in one.
More importantly, compared to Ac225, the other commonly used radionuclide used in alpha PRRT, the coherence of the daughter molecules of Bi212 to the somatostatin targeted vector is much stronger than the daughter molecules of Ac225. Hence the potential collateral damage by the errant daughter molecules is significantly less than Ac225. This makes the entire PRRT therapy much more targeted thus improving its effectiveness while making it safer.
Also, Pb212 has a sister diagnostic molecule that allows us to image the tumor and perform accurate dosimetry making the entire PRRT process more scientific and safer.
IS LEAD (PB212) PRRT AVAILABLE FOR PATIENTS?
Yes, Lead (Pb212) is available at FORTIS MEMORIAL RESEARCH INSTITUTE (FMRI), GURUGRAM (HARYANA, INDIA). FMRI is the only center in India that provides Lead (Pb212) PRRT therapy for patients with neuroendocrine tumors.
HOW IS THE TREATMENT ADMINISTERED?
On the day of the therapy, following a patient’s admission to the nuclear medicine ward, the doctors first administer an antiemetic intravenously. The patient’s vital signs are monitored by measuring blood pressure, pulse rate, and general well-being. The patient then receives two additional infusions containing a mixture of amino acids. These infusions protect the patient’s kidneys and minimize the effects of radiation by the radiopharmaceutical. The amino acid infusion continues for 4–5 hours.
30 minutes after the amino acid infusion, the radioactive peptide is administered. This takes anywhere between 5 to 15 minutes.
In the days following the treatment, some portions of the radioactive elements are expelled by the patient through urination. Doctors monitor the level of radioactive elements in the patient’s body until it falls to a ‘safe’ level. The patient is then discharged and their body’s radioactivity level is monitored until it has fallen to safe levels and the patient can be discharged.
During the week after the therapy, the patient is required to return to the medical center for measurements using a SPECT camera to determine the distribution of the radiopeptide in the body. This allows the physician to assess the irradiation of the kidneys and the cancer tissue.
Following the first cycle and subsequent PRRT treatment cycles, the patient’s blood is monitored for changes in white blood cell and blood platelet counts, and kidney function. These blood tests should be performed four weeks after each treatment cycle and two to four weeks before the next cycle.
WHAT ARE THE SIDE EFFECTS AND POTENTIAL RISKS INVOLVED IN THIS THERAPY
PRRT does have some temporary side effects.
- The most frequent side effects are mild reductions in the number of white blood cells and blood platelets. A decrease in the white blood cell count may result in infections. Blood platelets assist in the clotting of blood, so a decrease in platelet concentration may increase the risk of internal bleeding. In a few cases, the platelet count may fall to dangerous levels, which may require treatment and could lead to the postponement of the next treatment cycle.
Some more common side effects include:
- About 65% of patients receiving PRRT experience temporary hair loss (not baldness), but the hair will resume growing when the treatment is concluded. Over the longer term, a few patients may experience more serious side effects.
PRRT has several known side effects, which vary from person to person. Many of these will disappear after a short time, although others may be serious with longer-lasting and/or permanent effects on the body, and could indirectly be fatal.
During the therapy cycles, the patient may experience some or all of the side effects listed below. If the patient experiences any unexplained signs or symptoms, they should contact their physician to discuss their condition based on their risk profile.
Short-term side effects
(1) Nausea, vomiting, diarrhea, and adiarrheastion may occur during or immediately after therapy. These symptoms tend to disappear following the cessation of the amino acid infusion.
(2) Allergic reactions (itchy rash, anaphylaxis) may occur following the amino acid infusion with a plasma expander such as gelatin (Gelafusin®) during therapy.
(3) If the patient’s cancer is functionally active, the patient may experience a so-called carcinoid crisis during or following therapy due to the sudden release of hormones from the cancer cells into the bloodstream. This can cause circulatory and breathing difficulties, accompanied by headaches and other neurological symptoms. If this occurs, it is to be treated vigorously and may sometimes require short action short-acting medication.
Medium-term (commonly observed) side effects:
(1) Temporary decrease in the counts of red blood cells (erythrocytes) and white blood cells (leucocytes/ lymphocytes).
(2) Temporary decrease in blood platelets (thrombocytes).
Long-term (rarely observed) side effects
(1) Repeated administration of PRRT may result in serious deterioration of renal function in less than 1% of patients.
(2) Myelodysplastic syndrome (MDS) has been observed in less than 1% of patients and may be associated with prior chemotherapy.
(3) Other unknown deleterious effects may occur that have not been observed to date.
HAS PB212 PRRT BEEN USED IN CLINICAL PRACTICE?
Pb212 PRRT has been used, both in clinical trials in the USA as well as out of the clinical trial in Germany. These clinical studies have shown that PRRT with 212Pb is feasible, well tolerated, and substantially reduces tumor burden to patients with unresectable, metastatic SSTR-expressing NETs. Dramatic improvement in tumor burden and a positive impact on quality of life have been seen in all of the PRRT patients who received Pb212 PRRT at the highest dose tested.
WHY SHOULD I CHOOSE THE NUCLEAR MEDICINE THERAPY CENTRE AT FORTIS MEMORIAL & RESEARCH INSTITUTE (FMRI), GURUGRAM (HARYANA, INDIA)?
The department of Nuclear Medicine has a dedicated Therapy Unit where a host of Radioisotope therapies are routinely performed. The Department is one of the pioneers in Lutetium-based therapies for neuroendocrine tumors and was the first in the country to start Lutetium PSMA therapy. The nuclear medicine therapy center at FMRI is the only center in India offering Lead (Pb212) PRRT therapy for neuroendocrine tumors.
The Centre is also the first center to offer Targeted alpha therapy for neuroendocrine tumors, prostate cancer, and certain brain tumors. What sets the Nuclear Medicine Experts apart is their ability to personalize therapies while maintaining the highest safety ethical and quality standards