Prostate cancer and breast cancer are the most commonly diagnosed cancers in men and women in the United States, with nearly identical annual case numbers (about 314,000 for prostate cancer and 317,000). Both cancers are also major drivers of cancer-related deaths, second only to lung cancer. Yet, there’s a striking difference in how the two are screened: while breast cancer screening is routine and systematic, prostate cancer screening still lags behind.
Why is Prostate Cancer Screening Less Effective?
In both instances, breast and prostate screening catch about 70% of invasive cancers, but the main pathway for diagnosing prostate cancer—starting with a prostate-specific antigen (PSA) blood test, then a multiparametric MRI (mpMRI), and finally a biopsy—produces far more false positives than breast cancer screening. About 40% of prostate cancer screenings lead to a false positive, compared to only about 10% for breast cancer. This is partly because PSA tests simply reflect whether the prostate is getting larger, which can happen naturally with age, and not necessarily because of cancer.
Some doctors have tried to improve accuracy by looking at PSA density (PSA level divided by prostate size), but this only helps a little.
A Promising New Approach: PSMA-PET Imaging
At the European Association of Urology (EAU) Congress in London, UK, held March 13-16, 2026, researchers presented results from the Australian PRIMARY2 trial, which could change how prostate cancer is diagnosed. The trial explored whether adding a new imaging test—PSMA-PET/CT—to the standard diagnostic steps could help avoid unnecessary biopsies. [1]
This imaging scan uses a radioactive tracer attached to an antibody that seeks out the prostate-specific membrane antigen (PSMA), a protein found in much higher amounts on prostate cancer cells than on normal cells. When used after inconclusive MRI results, PSMA-PET/CT can make cancerous cells “glow” on the scan, making them easier to spot.
The randomized phase 3 PRIMARY2 study enrolled 660 men with inconclusive or ‘gray-zone’ MRI results, but who had other risk factors for prostate cancer, such as high PSA density or a strong family history. The men were randomly assigned (1:1) to either undergo a standard biopsy or to receive a PSMA-PET/CT scan first.
- If PSMA-PET was positive, patients underwent a targeted biopsy, either a standard-of-care transperineal systematic biopsy (n = 329) or an imaging-based strategy using pelvic [68Ga] Ga-PSMA-11 PET/CT (n = 331).
- Patients with a positive PSMA-PET outcome (n = 163), with a PRIMARY score of 3 to 5—underwent targeted biopsy guided by PSMA-PET and MRI findings.
- If PSMA-PET was negative (PRIMARY scores 1 or 2; n = 166), patients skipped the biopsy and entered a ‘watchful waiting’ (surveillance) program.
Key Findings
- Nearly half of unnecessary biopsies avoided: About 49% of men in the PSMA-PET group avoided biopsy because their scans were negative (95% CI, 44 to 55)
- No compromise in cancer detection: The rate of detecting clinically significant (potentially dangerous) prostate cancer was about the same in both groups.
- Fewer low-risk cancers detected: The PSMA-PET/CT approach cut the diagnosis of low-risk, likely harmless prostate cancers from 32% to 14%.
- Reproducible results: The interpretation of scans was highly consistent between different reviewers.
What Does This Mean for Patients?
“PSMA PET/CT scanning makes prostate cancer cells light up in a remarkable way, particularly in more aggressive cancers. It’s rare to see such strong imaging that could be so powerful in the clinic. Incorporating this testing into clinical care could help to address the major challenge of prostate cancer overdiagnosis, which leads to at best unnecessary and at worst harmful treatment for cancers that would never cause any harm,” explained James P. Buteau, MD, FRACP, FRCPC, who presented the study results during the European Association of Urology Congress.
“Getting told you have a risk of prostate cancer is a huge cause of anxiety and concern. Our findings show that PSMA PET/CT after MRI offers a ‘belt and braces’ approach that can determine which people have a clinically significant cancer, and which people are at low risk and don’t need a biopsy or further testing,” added co-lead investigator Louise Emmett.
The Future of Prostate Cancer Screening
The PRIMARY2 trial suggests that adding PSMA-PET/CT to the prostate cancer diagnostic pathway could make screening more accurate and less invasive—reducing unnecessary biopsies and the anxiety they cause, without missing dangerous cancers. This could bring prostate cancer screening closer to the systematic effectiveness of breast cancer screening, making it safer and more reassuring for patients.
“In summary, the addition of PSMA-PET to high clinical risk but inconclusive MRI halved the number of men requiring biopsy, and this led to a reduction of the diagnosis of insignificant malignancy without compromising the diagnosis of clinically significant prostate cancer,” Buteau summarized.
Long-term studies and further follow-up will help confirm these results—but for now, PSMA-PET/CT stands out as a promising step forward in smarter, more effective prostate cancer screening.
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Clinical trials
PSMA PET Additive Value for Prostate Cancer Diagnosis in Men With Negative/Equivocal MRI (PRIMARY2) – ClinicalTrials.gov ID NCT05154162
Reference
[1] Buteau JP, Moon D, Fahey MT, et al. Impact of [68Ga]Ga-PSMA-11 PET/CT in the diagnosis of prostate cancer in men with equivocal or non-suspicious findings on multi-parametric MRI (PRIMARY2): a multi-centre, phase III, randomised trial. Presented at: 41st Annual Congress of the European Association of Urology. London, UK. March 13-16, 2026
[2] Buteau JP, Moon D, Fahey MT, Roberts MJ, Thompson J, Murphy DG, Papa N, Mitchell C, De Abreu Lourenco R, Dhillon HM, Kasivisvanathan V, Francis RJ, Stricker P, Agrawal S, O’Brien J, McVey A, Sharma G, Levy S, Ayati N, Nguyen A, Lee SF, Pattison DA, Sivaratnam D, Frydenberg M, Du Y, Titus J, Lee ST, Ischia J, Jack G, Hofman MS, Emmett L. Clinical Trial Protocol for PRIMARY2: A Multicentre, Phase 3, Randomised Controlled Trial Investigating the Additive Diagnostic Value of [68Ga]Ga-PSMA-11 Positron Emission Tomography/Computed Tomography in Men with Negative or Equivocal Multiparametric Magnetic Resonance Imaging for the Diagnosis of Clinically Significant Prostate Cancer. Eur Urol Oncol. 2024 Jun;7(3):544-552. doi: 10.1016/j.euo.2023.11.008. Epub 2023 Dec 6. PMID: 38061976.
[3] Guo S, Kang F, Ma S, Jiao J, Ren J, Wang J, Zhang J, Qin W. The PRIMARY Score: Diagnostic Performance and Added Value Compared With MRI in Detecting Clinically Significant Prostate Cancer. Clin Nucl Med. 2024 Jan 1;49(1):37-44. doi: 10.1097/RLU.0000000000004951. Epub 2023 Nov 29. PMID: 38081190; PMCID: PMC11805474.
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DOI
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