A Clearer Map – and a Smarter Starting Point

Recent research points to a fundamental change in how prostate cancer may be diagnosed. Instead of starting with a blind biopsy, advanced PSMA-based imaging is moving to the very beginning of the diagnostic process. It can not only identify suspicious areas with high precision but also help determine whether a biopsy is needed at all – in the recent PRIMARY2 study reducing the number of biopsies by around 50% without missing clinically relevant cancers. Beyond that, PSMA imaging is now also used as a prognostic tool to predict how aggressive a tumor is likely to be – before any tissue is taken.

When prostate cancer is suspected, usually because of an elevated PSA level in the blood, the next step has traditionally been a „blind“ biopsy – 10–12 tissue samples taken at random from the prostate.

While the use of MRI before biopsy is increasing, it is not yet universal. And even when it is done, it often serves only as a mental map for the urologist rather than being directly used to guide the biopsy. As a result, the traditional approach can still miss serious cancers or create false alarms. At the same time, many men undergo biopsy unnecessarily, as a large proportion of elevated PSA findings do not correspond to clinically significant cancer. PSMA imaging has also been primarily used to stage cancer and determine its spread at a much later, often metastatic stage – until now.

But what if imaging came first and were used as a triage tool before biopsy – and biopsy only followed when truly needed and taken exactly from the spots detected by the imaging? Moreover, the PSMA scan is then also used to assess the risk of the tumour, an extremely important factor for deciding on the treatment path.

The two most recent studies: RAPID and PRIMARY2 – sought to test precisely this more advanced approach to the initial diagnosis. They used PSMA imaging (a high-tech PSMA PET/MRI scan in the case of RAPID and PSMA PET/CT in the case of PRIMARY2) right at the start to detect suspicious areas based on their PSMA expression and MRI criteria^[1]. The scan acted as a precise “treasure map” of the prostate, guiding doctors to take targeted biopsies from the concerning spots with a dedicated transrectal ultrasound PET/MRI fusion system^[1]. The goal was to determine whether this image-guided method is truly better than the standard “blind” biopsy at accurately detecting and staging prostate cancer. Secondary, but maybe even more importantly, non-invasive tumor characterization and prospective disease risk stratification using image-derived PSMA expression levels versus the invasive standard approach (biopsy) were evaluated. Whereas PRIMARY2 is still not finalized, RAPID has already unveiled the results after a median follow-up of 3 years.

The Key Results

Across both studies using PSMA PET imaging, several consistent findings emerge:

More accurate detection of clinically important cancer

PSMA-based imaging is excellent at identifying aggressive tumors. In image-guided approaches, 95% of clinically significant cancers classified as ISUP-GG ≥3 are detected.

More precise biopsies when they are needed

When a biopsy is performed, imaging allows it to be focused on the most suspicious areas. This improves diagnostic accuracy and reduces reliance on random sampling. Targeted image-guided biopsies detected additional cancers that random sampling missed – RAPID identified 15 additional cases, the majority of them clinically relevant.

Fewer unnecessary biopsies

When PSMA imaging is used as a first step, a substantial proportion of men with negative scans can avoid biopsy altogether. In practice, this can halve the number of biopsies, without compromising the detection of aggressive disease.

Fewer false alarms and better risk assessment

Non-invasive PSMA expression levels do not just detect cancer but also provide information about how aggressive it is likely to be. In follow-up over three years, imaging-based assessment in the RAPID study reduced the number of men incorrectly labelled as having aggressive cancer from 34 to 21, meaning significantly fewer false alarms and a lower risk of overtreatment.

Better prediction of disease course (prognosis)

PSMA imaging does not only detect cancer but also reflects its biological behaviour. The level of PSMA expression has been shown to correlate with tumor aggressiveness and patient outcomes as demonstrated by another recent study, PROMISE, by the Nuclear Medicine Department of the Medical University of Essen. This large retrospective study showed that PSMA-PET-based risk groups redefine prognosis in prostate cancer in 11,154 patients. This means that imaging can help predict how the disease is likely to progress – independently of traditional factors such as PSA or biopsy results – and help shape the treatment pathway.

Medical Practice

This imaging-first approach has several practical advantages for patients:

• Higher chance of detecting dangerous cancers early (with detection rates for aggressive disease around 95%),
• Lower chance of undergoing an unnecessary (and unpleasant) biopsy (potentially avoiding biopsy in up to half of cases),
• More accurate and earlier assessment of how serious the disease really is – even before biopsy results are available,
• Reduced risk of overtreatment and its side effects.

For the healthcare system it improves efficiency by avoiding unnecessary procedures and focusing resources where they are needed most. Admittedly, combined PET/MRI scanners are still relatively rare and expensive. However, a similar benefit can be achieved by combining two more widely available tests – a standard MRI and a separate PSMA PET/CT scan, precisely as demonstrated by PRIMARY2. When these images are fused, the result is nearly identical. This means that the shift toward imaging-first diagnosis can be implemented using existing technology in many clinical settings.

The Takeaway

PSMA-based imaging is no longer just a tool for staging prostate cancer – it is moving to the very start of the diagnostic pathway. By combining three roles – triage (who needs a biopsy), guidance (where to biopsy), and prognosis (how aggressive the disease is likely to be) – it offers a more precise, less invasive, and more efficient approach.

In practice, this creates a two-step strategy:

• Patients with a negative scan may safely avoid biopsy, supported by a negative predictive value of around 90% or higher for clinically significant cancer.
• Patients with a positive scan may undergo targeted biopsy, guided by imaging, or even move directly forward to targeted therapies, as PSMA-guided diagnosis is as reliable as invasive histological diagnosis

This marks a clear transition away from “blind” systematic biopsy toward a strategy where imaging defines the next step. In this new paradigm, biopsy is no longer the starting point, but a targeted confirmation step, if necessary anyhow.

 

Design of the Studies

RAPID

The study conducted in Austria by the Medical University of Vienna and University Hospital Krems with the participation of the Technical University of Munich involved 220 men suspected of having prostate cancer due to elevated PSA levels. All participants received the advanced PSMA PET/MRI scan. Then they were randomly split into two groups:

• The Standard or Random Biopsy (RB) Group: Doctors performed a standard 12-core random biopsy, unaware of the results of the PET/MRI scan.
• The Image-Guided Biopsy (IGB) Group: Doctors performed the same, blinded 12-core random biopsy, but also took 4 additional targeted biopsies from areas highlighted by the PET/MRI scan.
• Patients from the standard arm who had a negative “blind” biopsy, but a positive PET/MRI would "cross over" to receive an IGB.

Results were compared regarding detection rate, aggressiveness rating and prognosis of disease course in relation to cancer stage and follow-up.

PRIMARY2

The multi-centre Phase III study „co-led by Peter Mac and St Vincent’s Hospital Sydney recruited 660 Australians at higher risk of prostate cancer, due to their strong family history and other factors”, despite non-conclusive MRI findings (PI-RADS 2–3). Participants were randomly assigned to two groups:

• The Standard Biopsy (Control) Group: All patients undergo a standard template transperineal prostate biopsy (TPPB), independent of any additional imaging findings.
• The PSMA Imaging (Experimental) Group: Patients first receive a PSMA PET/CT scan, which is evaluated using a standardized scoring system.
  • Patients with a positive scan went on to have a targeted transperineal biopsy, focusing only on the suspicious areas identified by the imaging.
  • Patients with a negative scan did not undergo biopsy and are monitored clinically.

Results were compared in terms of detection rate of clinically significant prostate cancer, the number of unnecessary biopsies avoided, and patient outcomes including complications, quality of life, and long-term clinical course over a follow-up period of up to two years.

PROMISE / PPP3 (Prognostic Study)

This international, retrospective registry-based study included 11,154 men with histologically confirmed prostate cancer at all stages of disease, who underwent PSMA PET imaging between 2012 and 2024 across 35 centers worldwide. Patients were divided into development and validation cohorts based on site characteristics.

• Study Design: Clinical data and PSMA PET imaging findings were collected and combined to develop prognostic models (PPP3 nomograms) using advanced statistical methods. These models integrate imaging-derived parameters (PROMISE metrics) with clinical disease characteristics.
• Risk Stratification: Based on PSMA PET findings, patients were assigned to different risk groups reflecting their probability of survival at 3, 5, and 7 years. A simplified risk table was also created to allow practical clinical use.
• Comparison with Standard Models: The predictive performance of the PSMA-based models was compared with established clinical risk scores (e.g. EAU, NCCN).
• Outcome Measures: Results were evaluated in terms of overall survival prediction accuracy, with a median follow-up of 4.9 years.
• Key Result: PSMA-based prognostic models showed high predictive accuracy (c-index ~0.83–0.84) and were equal or superior to traditional clinical risk scores in predicting patient outcomes.

[1] RAPID

Bibliography

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The European Association of Urology. Press release: Scan that makes prostate cancer cells glow could cut need for biopsies. March 13, 2026

Peter MacCallum Cancer Centre. Scan reduces need for invasive prostate biopsies. March 13, 2026

ClinicalTrials.gov. PSMA PET Additive Value for Prostate Cancer Diagnosis in Men With Negative/​Equivocal MRI (PRIMARY2). May 28, 2025

GU Cast, Urology Podcast, PRIMARY 2 is positive! PSMA PET/CT moves to early detection, March 13, 2026