IN the fight against prostate cancer, one biomarker is proving to be a game changer.
According to Sunway Medical Centre Clinical Head and Nuclear Medicine Physician Associate Professor Dr Tan Teik Hin, the prostate-specific membrane antigen (PSMA) has transformed how doctors diagnose and treat the disease, offering patients better accuracy and targeted therapy.
"PSMA is our only biomarker for prostate cancer from the nuclear medicine perspective. We use it to scan the patient, and we also use it to treat the patient," he said in a health forum held in Sunway Medical Centre.
Around 80 per cent of prostate cancer cells express a high amount of PSMA on their surface, making it a reliable target.
Before treatment, patients undergo a PSMA PET-CT scan to determine whether their cancer cells are 'PSMA-positive.' Only then can targeted therapy be administered.
“We treat what we see, and we see what we treat. It’s a detect-and-destroy strategy,” Dr Tan explained.
PSA vs PSMA
Dr Tan highlighted a common misconception between PSA (prostate-specific antigen) and PSMA (prostate-specific membrane antigen). While their names are similar, their roles are very different.
“PSA is a protein found in the blood. A high PSA level may indicate prostate cancer, but it doesn’t tell you where it is. PSMA, on the other hand, is expressed on the cancer cell surface and can be detected through imaging,” he said.
This is where PSMA PET-CT comes in. Unlike conventional CT or MRI, PSMA PET-CT offers a hybrid imaging technique that combines structural mapping with highly sensitive detection.
“Think of it as a GPS. The CT gives us the map of the body, while the PET highlights the exact location of the tumor. It can detect tumors as small as 0.3 cm,” Dr Tan said.
An Australian study known as the pro-PSMA trial found that PSMA PET-CT was 27 percent more accurate than conventional imaging, helping doctors better understand how far the cancer has spread, whether to the bones, lungs, or liver.
Targeted therapy with fewer side effects
Once a patient is confirmed as PSMA-positive, the next step is radionuclide ligand therapy, which is a targeted treatment that delivers radiation directly to cancer cells while sparing surrounding tissues.
“The principle is simple. First, you identify the target with imaging. Then you deliver the radioactive ligand to bind to those cells. After treatment, another scan, called SPECT-CT, is done to evaluate how well the therapy worked,” he said.
According to the expert, this form of nuclear medicine is not entirely new. Radioactive iodine has been used for nearly two decades to treat thyroid cancer. What’s new is the ability to adapt this targeted therapy for prostate cancer and neuroendocrine tumors.
“Studies have already shown that PSMA-based treatment can delay disease progression, prolong survival and improve quality of life for patients,” Dr Tan noted.