PSMA PET-CT is the most accurate staging scan for prostate cancer — far superior to conventional CT and bone scan. It detects spread to lymph nodes and bones that older imaging methods completely miss.
Your urologist has recommended a PSMA PET-CT scan. You may have heard of PET scans but "PSMA" is new to you. Perhaps you have already had a CT scan and a bone scan, and you are wondering why another imaging test is needed.
The answer is that PSMA PET-CT is a completely different class of investigation — one that has transformed prostate cancer staging in the last decade. This article explains what it is and what it can tell you.
1. What is PSMA PET-CT?
PSMA stands for Prostate-Specific Membrane Antigen — a protein that is overexpressed on the surface of prostate cancer cells. Critically, PSMA is expressed in proportion to cancer aggressiveness: more aggressive, higher-grade tumours express more PSMA, making them particularly visible on the scan.
PSMA PET-CT combines two technologies:
- PET (Positron Emission Tomography): Detects gamma rays emitted by a radiotracer injected into the bloodstream
- CT (Computed Tomography): Provides anatomical reference — showing the body's structure so the PET signal can be accurately localised
A PSMA-targeting ligand (most commonly Gallium-68 PSMA or PSMA-1007) is attached to the radiotracer. This compound seeks out PSMA-expressing cells throughout the body — wherever there is prostate cancer, it accumulates and creates a bright "hot spot" on the PET scan.
2. How it works
After intravenous injection, the PSMA tracer circulates through the bloodstream and attaches to PSMA molecules on prostate cancer cells. Cancer deposits — even those only a few millimetres in diameter — accumulate enough tracer to produce a detectable PET signal. The CT component simultaneously provides the anatomical location of these signals.
A CT scan identifies lymph node spread by measuring lymph node size — nodes over 10mm are considered suspicious. A PSMA PET can detect cancer in nodes that are completely normal in size. This is game-changing: many patients previously staged as "node-negative" on CT were actually node-positive on PSMA PET.
3. PSMA vs conventional staging scans
- CT detects lymph node enlargement (>10mm)
- Bone scan detects bony metastases
- Misses up to 40% of node-positive disease
- Bone scan poor sensitivity for early bony disease
- Requires 2 separate appointments
- No molecular targeting
- Detects cancer in normal-sized nodes
- Full-body metastasis assessment in one scan
- Superior sensitivity at low PSA levels
- Detects bone metastases earlier than bone scan
- Single 2-hour appointment
- Molecular targeting — prostate cancer specific
4. Who needs a PSMA scan?
Initial staging — before surgery or radiation
PSMA PET-CT is increasingly the standard first-line staging investigation for high-risk prostate cancer (Gleason 8–10, PSA >20, or T3 disease on MRI). It detects lymph node and bony spread before local treatment — allowing the treatment plan to be modified if metastatic disease is present.
Biochemical recurrence — PSA rising after treatment
This is where PSMA PET has had the greatest impact. When PSA rises after prostatectomy or radiation and conventional CT and bone scan are negative (as they often are), PSMA PET can detect the site of recurrence at PSA levels as low as 0.2–0.5 ng/mL — something impossible with older imaging. This allows targeted salvage treatment rather than systemic therapy.
Before metastasis-directed therapy
For oligometastatic prostate cancer (a small number of metastases), PSMA PET identifies all sites of disease so they can be targeted with stereotactic radiation (SBRT) — potentially delaying the need for systemic hormone therapy.
5. What to expect during the scan
Preparation
No fasting required for most PSMA tracers. Avoid vigorous exercise 24 hours before. Hold diuretics on the day if prescribed. Drink well to stay hydrated.
Injection and uptake
A small intravenous injection of the radiotracer is given. You wait 45–60 minutes in a quiet room for the tracer to distribute through the body and bind to PSMA-expressing cells.
Scanning
You lie flat on the scanner table for 20–30 minutes while the combined PET and CT images are acquired. The machine is not an enclosed tunnel — it is an open ring. No claustrophobia risk for most patients.
After the scan
You can eat, drink, and drive normally immediately after. Drink plenty of fluids to flush the radiotracer, which is excreted in the urine. The radiation dose is modest — comparable to a few weeks of natural background radiation.
6. Interpreting the results
The nuclear medicine physician and radiologist report the scan together. Key findings include:
- No distant disease detected: The most common result in localised prostate cancer. Treatment proceeds as planned.
- Pelvic lymph node involvement: Changes surgical planning — extended lymph node dissection is included; radiation field may be expanded.
- Para-aortic or mediastinal nodes: Suggests more widespread lymphatic spread; systemic therapy considerations arise.
- Bone metastases: Localised bone disease may still allow metastasis-directed therapy. Widespread bone metastases indicate systemic treatment is the priority.
- Visceral metastases (lung, liver): Uncommon. Indicates hormone-resistant or highly aggressive disease.
7. Availability in India
India is actually well-positioned for PSMA PET imaging. Gallium-68 PSMA PET-CT is available at major oncology centres in Delhi, Mumbai, Bangalore, Chennai, Hyderabad, and Pune. The scan is performed at nuclear medicine departments attached to oncology hospitals or standalone PET centres.
Cost is typically ₹25,000–45,000 and the scan is increasingly covered under insurance policies for patients with established prostate cancer diagnoses. Ask your urologist for a referral to the nearest facility.
- Do I need staging scans — or is my cancer low enough risk to proceed without them?
- Should I have PSMA PET rather than a conventional CT and bone scan?
- Which PSMA tracer is available at your preferred centre — Ga-68 PSMA or PSMA-1007?
- How will the results change my treatment plan?
- If I have a rising PSA after surgery, at what level do you recommend a PSMA PET?
- Is there a centre near me that you would recommend?
This article is for general patient education about PSMA PET-CT imaging. Whether a PSMA scan is appropriate in your case depends on your specific clinical situation. Discuss with your urologist or oncologist.