When a "Clear" Scan Isn't the Whole Story: The Case for a Second PSMA PET
Second PSMA PET Scan Finds Hidden Prostate Cancer in 56% of Patients
Informed Prostate Cancer Support Group • Imaging & Recurrence
Bottom Line Up Front
If your PSA is climbing after surgery or radiation but your first PSMA PET scan came back "negative," that scan is a snapshot in time — not a verdict. In a new study of 210 men whose first scan showed nothing, a second PSMA PET scan later found cancer in 56% of them, and the new information changed the treatment plan for nearly half. The men most likely to benefit had a higher PSA or a PSA that doubled in under 12 months. The practical message: a single clear scan doesn't close the book. Keep tracking your PSA, and talk with your care team about the right time to look again.
What the researchers found
The study was published in the July 2026 issue of The Journal of Nuclear Medicine and announced by the Society of Nuclear Medicine and Molecular Imaging (SNMMI) on July 7, 2026. A team led by Dr. Ur Metser at the University of Toronto and Princess Margaret Cancer Centre asked a straightforward question that, surprisingly, had almost no published answer: if a man's first PSMA PET scan is negative, is it worth repeating later?
They drew on the Registry for Recurrent Prostate Cancer in Ontario, a large database of men recruited between October 2018 and September 2022. Out of 4,140 registry patients, they identified 210 men who fit the profile: rising PSA after first-line treatment (prostatectomy or radiation), a negative first scan, and at least one repeat PSMA PET scan afterward. They then compared the two scans head to head — positivity, PSA level, PSA doubling time, and whether the results changed care.
The biggest impact on treatment came in men found to have oligometastatic disease — a small number of cancer spots (fewer than five). Finding a limited number of tumors matters because it can open the door to treatments aimed directly at those specific sites, such as targeted (stereotactic) radiation, rather than jumping straight to therapies that affect the whole body.
Why a "negative" scan doesn't mean "no cancer"
Think of a PSMA PET scan the way an engineer thinks about a detector with a noise floor. The scan works by attaching a radioactive tracer to PSMA, a protein that sits on the surface of most prostate cancer cells, then photographing where that signal collects. But every detector has a threshold below which a real signal is indistinguishable from background. Early recurrence can be too small, too faint, or expressing too little PSMA to rise above that floor.
A "negative" result, then, isn't proof the cancer is gone — it means the disease, if present, is still below the detection threshold. Give it time, let the tumor grow and the PSA climb, and the same detector may now pick up a signal it genuinely could not see before. That is exactly what the second scans captured.
This is not a rare corner case. Even with today's excellent PSMA tracers, about 30% of men with a suspected recurrence have nothing visible on their first scan despite a rising PSA. For those men, the question of "what next?" has been genuinely hard — and this study is one of the first to give it a data-backed answer.
A real example from the study
One patient's timeline
A 58-year-old man had his prostate removed (pathology: pT2a, node-negative, clean margins), then later received salvage radiation to the prostate bed. When his PSA began rising again, he had a PSMA PET scan at a PSA of 0.57 ng/mL — and it showed nothing. Reasonable plan: watch and wait.
One year later his PSA had climbed to 2.72 ng/mL, with a doubling time of just 5.3 months — a fast, worrying pace. A repeat PSMA PET now lit up a single spot in the L1 vertebra (a small bone metastasis). That one finding flipped his plan from observation to targeted radiation aimed precisely at that deposit. Same patient, same technology — the difference was time and a growing signal.
Who is most likely to benefit from a repeat scan?
The study's findings line up with a broader body of research showing that PSMA PET detection rises steeply with PSA. The tracer needs enough disease to see; the higher and faster the PSA, the more likely a scan is to find something. Recent studies give a sense of the pattern:
| Setting | Roughly how often PSMA PET is positive |
|---|---|
| Very low PSA (0.2–0.5 ng/mL after surgery) | ~50–57% |
| PSA around 1 ng/mL | ~75% |
| PSA above ~1.5–2 ng/mL | ~90% or higher |
Across these studies, the same three factors keep surfacing as predictors of a positive scan: higher PSA, shorter PSA doubling time, and higher-grade disease. That is why your care team watches the trend in your PSA, not just a single number — the slope often matters as much as the value.
Practical takeaways for patients
- A negative scan is a "not yet," not a "never." If your PSA keeps rising, the conversation about re-imaging should stay open.
- Timing is a strategy, not an afterthought. Many experts suggest repeating the scan once the PSA has meaningfully risen or doubled, because that is when a faint recurrence becomes visible. Some guidelines suggest waiting until PSA reaches certain thresholds before scanning at all.
- Ask what a positive scan would change. A scan is most valuable when the result would actually alter your plan — for example, enabling targeted radiation to a few spots instead of whole-body therapy.
- Expect a prior-authorization step. A repeat PSMA PET is not automatically approved just because PSA is rising. Insurers typically want documentation of your PSA trend and the medical reason for re-imaging, so it helps if your physician spells out the rationale.
The bigger picture: the tools keep improving
Part of why repeat imaging is now a realistic option is that PSMA PET itself has matured rapidly. In the U.S., three PSMA-targeted tracers have reached the market: Ga-68 PSMA-11 (approved December 2020), Pylarify / piflufolastat F 18 (May 2021), and Posluma / flotufolastat F 18 (May 2023). A newer Pylarify formulation (marketed as Pylarify TruVu) has since been approved to streamline manufacturing and broaden access. Scanner hardware is advancing too — newer long-axial-field-of-view PET systems are more sensitive and are pushing detection down to lower PSA levels than before.
One note for the financially minded: the PSMA imaging market has also become competitive and, at times, contentious. In 2025, Lantheus (maker of Pylarify) faced shareholder class-action lawsuits alleging the company did not adequately disclose how a 2025 price increase might affect Pylarify's competitive position, and the company has separately been navigating patent litigation tied to a therapeutic asset. These are business and securities matters — they concern corporate disclosures and pricing, not the safety or accuracy of the scans themselves — but they are worth knowing about as the field's economics evolve and as patients weigh cost and access.
Honest limitations
This was a registry study, not a randomized trial. It tells us that repeat scans frequently find disease and frequently change plans, but it was not designed to prove that acting on those findings makes men live longer or better — that is the next question the field needs to answer. The right timing for a repeat scan still depends on the individual: your PSA level and velocity, your original disease, your overall health, and what treatments are on the table. Use this evidence to inform a shared decision with your care team, not to demand or refuse a scan on its own.
Verified sources
- Metser U, Bauman G, Rashid M, Mirshahvalad SA, Kohan A, Green B, Chan R, Hamilton R. "Utility of PSMA PET/CT After an Initial Negative Scan: Results from a Prospective Multicenter PSMA PET Registry." Journal of Nuclear Medicine. 2026 Jul;67(7):1097–1101. DOI: 10.2967/jnumed.126.272204. https://jnm.snmjournals.org/content/67/7/1097
- Society of Nuclear Medicine and Molecular Imaging. "Second PSMA PET changes treatment for nearly half of prostate cancer patients." News release, July 7–8, 2026 (via EurekAlert!). https://www.eurekalert.org/news-releases/1135417
- SNMMI original release. snmmi.org/Web/News/Articles/Second-PSMA-PET-Changes-Treatment-for-Nearly-Half-of-Prostate-Cancer-Patients
- Radiology Business. "2nd PET scan changes treatment for nearly half of prostate cancer patients." July 2026. radiologybusiness.com
- UroToday. "APCCC Diagnostics 2025: Biochemical Recurrence — When Do You Image?" (Detection ~77% at PSA <2 ng/mL above nadir, ~93% at >2 ng/mL, post-radiotherapy.) urotoday.com
- Thomas S, Callahan J, Conway P, et al. "High Detection Rates for PSMA-avid Prostate Cancer Recurrence at Low PSA Levels on Extended Axial Field-of-view PET/CT." European Urology Open Science. 2025 Jan;71:49–56. doaj.org/article/caa98b1679824771a90c5402f125d896
- "[18F]PSMA-1007 PET/CT in biochemical recurrence after radical prostatectomy." PLOS One. 2026. (Detection 56.5% at PSA 0.2–0.5 to 90.5% at PSA ≥1.5 ng/mL; predictors: PSA, ISUP grade, PSA doubling time.) journals.plos.org
- AuntMinnie. "PSMA-PET imaging spiked after FDA approval." Jan 2025 (tracer approval dates: Ga-68 PSMA-11 Dec 2020; Pylarify May 2021; Posluma May 2023). auntminnie.com
- OncLive. "FDA Approves Pylarify TruVu for PSMA-PET Imaging in Prostate Cancer." June 2026. onclive.com
- AJMC. "FDA Approves First Radiohybrid PSMA-Targeted PET Imaging Agent for Prostate Cancer" (flotufolastat F 18 / Posluma). ajmc.com
- Radiology Business (legal news). "Lantheus misled investors about blockbuster imaging agent, class action lawsuit claims." Sept 2025. radiologybusiness.com
- Lantheus Holdings. "FDA Acceptance of NDA for New Formulation of Market-Leading PSMA PET Imaging Agent" (PDUFA action date March 6, 2026). Aug 6, 2025. lantheusholdings.gcs-web.com
Prepared for IPCSG members as general educational information, not medical advice. It summarizes published research and public releases as of July 2026; findings and product availability may change. Decisions about imaging and treatment should be made with your own physicians, who know your full history. Note: sources 5–7 report detection rates in the general biochemical-recurrence setting and provide context; they are not from the Metser study, which specifically studied men whose first scan was negative.
Comments
Post a Comment