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177Lu PSMA-617 Therapy, (Pluvicto)

177Lutetium PSMA-617 (brand name Pluvicto) is a type of therapy known as PSMA (prostate-specific membrane antigen) targeted ligand therapy. It is prescribed for patients diagnosed with hormone-resistant metastatic prostate cancer that progressed while on chemotherapy. This document provides background on how the treatment works as well as information on the risks and side effects, how to prepare for the treatment, and what to expect. Finally, radiation precautions will be discussed.

Background

177Lu PSMA-617 is a therapeutic drug that delivers beta-particle radiation selectively to cells with high expression of PSMA receptors. It makes use of a ligand (PSMA-617) that has a radioactive material (177Lu) attached to it. More PSMA receptors are present in tumor cells than in normal cells. When the radioactive ligand binds to the PSMA on the tumor cells, it brings the radiation directly to the tumor cells no matter where they are located in the body. Think of them as a "lock and key" combination, with the lock being the receptor on the cell surface (PSMA) and the key being the 177Lu-PSMA-617 (radiopharmaceutical). This agent offers both diagnostic and therapeutic capabilities. The combination of a diagnostic radiotracer followed by administering a therapeutic dose is known as theranostics (Therapy and Diagnostics ). Theranostic agents offer precise radiation targeting mechanisms. The goal of the treatment is to deliver enough radiation to the tumor cells to significantly decrease their growth and kill as many of them as possible.

How the Treatment Works

Diagnosis. The diagnostic part of the procedure uses 68Ga PSMA-11 (Locametz®) or 18F-PSMA-DcPyl (Pylarify®). The PSMA ligand is similar to the one used for therapy but uses a different type of radioactive material that provides an image (PET/CT) to show where the tumor is and how well the ligand attaches to it.

For this procedure, you will receive an injection into an arm vein and will wait 45-60 minutes to allow it to circulate before undergoing  the scan. The actual scan takes about 30 minutes, and we do not expect you to experience any side effects. Once the scan is completed, the nuclear medicine doctor/radiologist will talk to your oncologist, arrange a time to meet, and set up a schedule for your therapy if needed.

Treatment. The therapy procedure consists of up to 6 treatments of 177Lu PSMA-617. Each treatment will take 1-2 hours. On the day of treatment, you will be encouraged to drink plenty of water. If needed, you will be given an infusion of fluids to help your body get rid of the extra radioactive ligand.

The medication will be administered via an arm vein. Though there are different methods to inject the radioactive therapy, all methods are relatively short, and the administration takes only about 10-30 minutes. Before leaving the hospital, you will  be asked to empty your bladder. This is done because the main way your body gets rid of the extra radioactive peptide is through your urine. There is no need to stay in the hospital overnight.

Side Effects

  • The main side effects of this treatment are fatigue and dry mouth. To help with dry mouth, your physician may encourage you to use ice packs on your cheeks.
  • The radiation may cause a decrease in your red cells, white cells, platelets, liver or kidney function. These will be monitored during the course of your therapy.
  • As the radiation begins to have an effect on the tumor, it may cause inflammation of the tumor, which may cause pain. This may be particularly noticeable if you have tumor in your bones and other organs. You may need to take some mild pain medication.
  • You may feel a bit more tired for a few weeks after the therapy.
  • It is also possible you may not have any of these symptoms.

How to Prepare

Since the therapy will take 1-2 hours, you should wear comfortable clothing. You will be sitting in a chair or lying in a bed. Since the medicine washes out from your body by the kidneys, you will be asked to drink plenty of fluids before arrival and on discharge.

Several days before each treatment, you will need to undergo blood to make sure it is safe to proceed. These include tests for your red cells, white cells, platelets, liver and kidney function. 

Radiation Effects and Precautions

The treatment agent (177Lu PSMA-617) delivers beta-radiation (B-) which ablates (destroys) the cancer cells. The B- radiation travels a few millimeters from where it locates. The treatment also delivers gamma radiation that can escape your body and reach others around you. This amount will be measured before you leave the department, and you will receive instructions for appropriate precautions. You may need to stay and sleep in a separate room for a day or two after the therapy. The nuclear medicine doctor/radiologist will let you know what precautions to take and for how long.

For about one week, the extra treatment agent will be in your urine. It is important that during this time you practice good bathroom cleanliness. No one should be able to use your washcloth, toothbrush, or other items. You are encouraged to sit to urinate to avoid splashing. Flush twice after using the toilet. If you spill any urine, wipe it up and flush it down the toilet. Wash your hands well after going to the bathroom. You should also avoid intimate contact during this time.

Pregnancy

We recommend not fathering a child for 3 months following the treatment.

Follow Up

  • Since the treatment agent is injected into the vein, it will reach your entire body and treat cells wherever they are located. Some of the radiation may cause effects on the bone marrow, causing a decrease in the red cells, white cells, and platelets. The kidneys also receive some of the radiation since urine is the primary mode of excretion. The nuclear medicine physician/radiologist and your oncologist will monitor these blood values during your treatment.
  • Your nuclear medicine physician/radiologist and your oncologist will also monitor your PSA level. A decrease in PSA levels during treatment will indicate a good response.

Diet and Nutrition

Drink plenty of liquids such as water or juices. Urinating frequently and drinking more fluids will help the excess treatment agent to leave your body more rapidly, thus lowering the amount of radiation to other parts of your body.