Prostate cancer is one of the most common types of cancer in men. Choosing the right imaging method during the diagnosis, staging, and post-treatment follow-up stages is critical for treatment success. In recent years, PET PSMA imaging, developed in the field of nuclear medicine, has become one of the gold standard methods for the detection and follow-up of prostate cancer.
What is PET PSMA?
PET PSMA is a positron emission tomography (PET) examination performed using a special radiopharmaceutical developed against Prostate-Specific Membrane Antigen (PSMA). PSMA is a protein found in much higher amounts on the surface of prostate cancer cells compared to normal tissues. This feature allows cancer cells to be distinguished through imaging.
Working Principle
The low-dose radioactive labeled PSMA molecule, administered to the patient intravenously, distributes throughout the body via the bloodstream. It selectively binds to prostate cancer cells where the PSMA receptor is dense. The PET-CT or PET-MR device images the areas where this radioactive accumulation occurs with high resolution. Thus, even millimetric cancer foci can be detected.
In Which Situations Is It Used?
PET PSMA imaging is used at many stages in the management of prostate cancer:
- Initial staging in high-risk prostate cancer
- Detection of the location of the disease in biochemical recurrences where PSA levels rise again after treatment
- Evaluation of bone, lymph node, or other organ metastases
- Providing additional information in cases where classical bone scintigraphy, CT, and MR are insufficient
- Determining radiation therapy fields in treatment planning
- Monitoring treatment response after hormone therapy or radiotherapy
- Selection for targeted PSMA radioligand therapy in eligible patients
Advantages of PET PSMA
- Much higher sensitivity and specificity compared to classical imaging methods
- Ability to detect microscopic recurrences even at low PSA levels
- Visualization of both soft tissue and bone metastases in a single examination
- Directly influencing the treatment plan to prevent unnecessary procedures
- Clearly revealing the extent of the disease by performing a whole-body scan
- Paving the way for personalized treatment options such as radioligand therapy
- Rapid elimination of the radioactive substance used from the body
Treatment (Imaging) Process
The PET PSMA examination is performed by experienced teams in nuclear medicine units. Before the procedure, the patient is provided with detailed information about the examination.
Preparation and Application
It is recommended that the patient drinks plenty of water before the examination. An intravenous line is opened, and the PSMA-bound radioactive substance is administered intravenously. A resting period of approximately 60 minutes is required for the substance to distribute in the body and bind to target cells. Afterward, the patient is placed in the PET-CT device and scanned in a supine position for approximately 20-30 minutes. The procedure is painless.
After the Examination
The patient can return to their daily life after the procedure. Consuming plenty of water helps the radioactive substance to be excreted faster through urine. The evaluation of the examination is performed by a nuclear medicine specialist, and the result report is interpreted together with the urology or oncology team.
Points to Consider
- The radiation dose used is at a level similar to classical PET examinations and is safely applied when necessary
- Close contact with small children and pregnant women should be limited for the first few hours after the procedure
- Existing medications, allergy history, and kidney functions must be reported to the physician before the procedure
- In patients receiving hormone therapy, the timing of imaging is adjusted according to the treatment plan
- Results must be interpreted together with clinical findings, PSA levels, and other examinations
- PET PSMA does not always eliminate the need for a biopsy; in some cases, a biopsy may be required for confirmation
Difference of PET PSMA from Classical Imaging
Traditionally, the spread of prostate cancer was evaluated with bone scintigraphy, computed tomography, and magnetic resonance (MR) imaging. However, these methods may be insufficient in detecting recurrences, especially at low PSA levels. Since PET PSMA targets PSMA receptors on the cell surface, it can detect even millimetric tumor foci.
In this way, unnecessary radiotherapy fields, unnecessary surgical interventions, and incorrect treatment planning are largely prevented. By clearly seeing the true extent of the disease, the physician can make an evidence-based treatment decision.
Frequently Asked Questions
- Do I need to be fasting before the examination? Usually, it is not necessary to fast for a long time; centers provide specific preparation instructions to patients.
- How long does the procedure take? It takes an average of 1.5-2 hours from the administration of the substance to the end of the scan.
- Are there any side effects? The radioactive substance used is at a very low dose and does not cause serious side effects.
- How soon are the results available? They are usually provided as a detailed report on the same day or within a few business days.
Effect of PET PSMA Results on Treatment Plan
PET PSMA imaging plays a major role not only for diagnostic purposes in prostate cancer management but also in guiding treatment decisions. While evaluating the suitability of surgical or radiotherapy options in localized disease, it helps in planning systemic treatments (hormone therapy, chemotherapy, targeted therapies) in metastatic disease.
PET PSMA imaging is necessary for the application of current nuclear medicine-based treatment options, especially 177Lu-PSMA radioligand therapy. In this way, it is determined in advance which foci in the disease are suitable for treatment, and a personalized treatment plan is created. Interpretation of imaging results by an experienced multidisciplinary team is critical for the success of the treatment.
The Role of PET PSMA in Other Cancer Types
Although the PSMA receptor is found in high amounts in prostate tissue as the name suggests, studies conducted in recent years have shown that the PSMA receptor can also be found in some other tumor types, primarily thyroid, kidney, and some breast cancers. For this reason, PET PSMA imaging can provide valuable information in the evaluation of different cancer types in selected cases.
However, its area of use is primarily limited to prostate cancer and it is not a routine imaging method for other cancers. Which PET examination should be performed on which patient is determined according to the current disease type, stage, clinical findings, and treatment plan. A multidisciplinary evaluation process is critical for the physician to make the right imaging choice.
PET PSMA at Koru Hospital
As Koru Hospital, we offer PET PSMA imaging in the diagnosis, staging, and treatment follow-up of prostate cancer to our patients with the cooperation of our experienced nuclear medicine, urology, and oncology teams. With our modern PET-CT infrastructure, multidisciplinary tumor board, and personalized treatment planning, we determine the most appropriate approach for each patient's disease; we aim to provide a care approach that prioritizes quality of life with the principle of accurate diagnosis and accurate treatment.
