Prostate Specific Membrane Antigen (PSMA) Radioligand Treatments For Prostate Cancer.

Prostate Specific Membrane Antigen

Prostate cancer is one of the most common cancers among men. An approximate 1 in 9 men will be diagnosed with prostate cancer in his lifetime, and it is one of the leading causes of cancer death in men. While the majority of prostate cancers are early stage at diagnosis, a significant portion will have regional or distant metastases.

Prostate Specific Membrane Antigen (PSMA) Radioligand Therapy is a targeted radiotherapy treatment for patients who typically have metastatic castrate resistant prostate cancers.

PSMA is a type II transmembrane glycoprotein that is found in concentrations 100-1000 times higher in prostate cancers as compared with normal tissue.

Hence, PSMA provides a good target for radionuclide treatment, as is it highly expressed in prostate cancers. We are able to direct very higher doses of radiation to prostate cancer cells while limiting radiation exposure to normal tissue.

The more commonly used radioactive isotopes in radioligand treatments are Lutetium 177 and Actinium 225. These radioactive isotopes emit beta and alpha particles respectively, which cause ionizing radiation and result in DNA damage and eventual cancer cell death.

The treatment is usually done on an outpatient basis, and is expected to take approximately 4-6 hours in total. The PSMA radioligand treatment is given as a slow intravenous infusion over 20 minutes, which will be followed by a normal saline infusion. No immediate side effects or complications are expected during the administration of the radioligand.

There are some potential side effects from the treatment. Some patients may experience nausea and fatigue after the treatment, which can last for up to 1 month after treatment.

Approximately 10-20% of patients will experience drop in blood cells (e.g. red blood cells, white blood cells, platelets), which is typically transient in nature (approximate 6 weeks), with recovery of blood levels expected.

Approximately 10-20% of patients will experience a decrease in salivary production (xerostomia).

PSMA radioligand treatments are used to reduce overall tumor volume and halt the cancer progression.

PSMA radioligand treatments have demonstrated biochemical responses in patients, and have shown trends towards longer progression free survivals and overall survivals, but with generally better side effect profiles as compared with chemotherapy treatment options.

The treatment currently is often used in heavily pre-treated patients with extensive bony metastases and even visceral metastases. However, there is increasing data that show patients who undergo Lu177 PSMA treatments earlier have better outcomes as compared to heavily pretreated populations.