If you have metastatic castration-resistant prostate cancer (prostate cancer that has spread outside the prostate and is no longer responsive to traditional hormone therapy) and you have already received first and second-line treatments, a new, FDA-approved therapy may be something for you and your cancer doctor to consider. This is called prostate-specific membrane antigen (PSMA) radioligand therapy.
PSMA is a protein on the surface of prostate cancer cells. By using a PET/CT scanner and an intravenous injected radiotracer that specifically targets this protein, doctors can see where prostate cancer is located anywhere in the body. Based on the results of this PSMA PET/CT scan, and if you’ve had other treatments for metastatic castration-resistant prostate cancer, you may be a candidate for PSMA radioligand therapy. Data from clinical trials suggest that about 70% of men may be eligible for PSMA radioligand therapy.
What is Lutetium-177 (PSMA Radioligand Therapy)?
In PSMA radioligand therapy, the PSMA targeting molecule (which is similar to the one used for PET scan imaging) guides the treatment to target the cancer cells and kill them. While other molecules are being developed, so far, lutetium-PSMA (Lu-PSMA) is the only FDA-approved PSMA-targeted radioligand. Lu-PSMA consists of the PSMA targeting molecule linked to lutetium-177 (Lu-PSMA), a heavy metal that gives off radiation that kills the cancer cells. One of the main benefits of this type of radiation therapy is that the radiation only travels about 1 mm. Because of this short distance, there is minimal damage to surrounding normal cells. The main goals of treatment are to decrease pain, fatigue, and other symptoms that may be related to prostate cancer. Additional goals include decreasing the size and growth of the prostate cancer and improving quality of life. To check if treatment is working, your doctor will schedule routine symptom checks, blood work, and imaging.
What to Expect During Treatment
PSMA radioligand therapy is done on an outpatient basis. This typically involves several trips to the cancer treatment facility. Treatment is given every 6 weeks and patients can receive up to 6 cycles of treatment.
On “treatment day” (Day 1), it is important to drink plenty of fluids. After an IV is inserted in your arm, you will receive the treatment injection (this takes about 15-20 minutes) followed by additional IV fluids. You will be able to go home after you urinate and the radiation in your body is measured at a safe level (typically 3 hours after the treatment). On “scanning day” (Day 2), you return to the cancer center for a SPECT/CT scan to check the effectiveness of the treatment. A nuclear medicine specialist will discuss the results with you.
What are the Side Effects of PSMA Radioligand Treatment?
The majority of side effects from PSMA radioligand treatment are well tolerated and will not vary much from the side effects you’ve had with previous treatment. Mild side effects may include:
- tiredness
- nausea
- dry mouth
- dry eyes
- reduced hemoglobin (anemia)
- reduced platelets (thrombocytopenia)
- vomiting
- loss of appetite
- increased risk of infection
- reduced kidney function
One potential long-term side effect may be an increased risk of developing another cancer secondary to radiation treatment. However, this risk is quite low in someone with advanced prostate cancer.
Important Radiation Safety Notes
Because PSMA radioligand therapy involves the use of radioactivity, you are “radioactive” for a period of time — the most during the first 2 hours after treatment. Most of the radiation leaves the body in the urine over time.
For up to 5 days after treatment, it is important to avoid close contact with anyone for more than 2 hours a day. Also, try to leave about 6 feet of space between you and others. This is especially important if you are around pregnant women and young children. In this case, try to spend no more than about 15 minutes per day together and, again, stay about 6 feet apart.
For 3 nights after treatment, you should not sleep in the same bed as another person. We also recommend sitting to urinate in order to limit urine splashing because this is how the radioactivity leaves the body. Also, clean the toilet several times per week.
PSMA radioligand therapy is an exciting new treatment option for men with metastatic castration-resistant prostate cancer. If you think you are a candidate for this treatment, discuss your eligibility with your doctor. Plus, there are ongoing clinical trials using PSMA radioligand therapy in earlier prostate cancer disease states — for example, metastatic hormone-sensitive prostate cancer. You might be interested in some of them and be eligible to participate if you meet the study requirements.