Health
A Second PSMA PET Scan Finds Hidden Prostate Cancer in Over Half of Patients
A negative scan is supposed to be reassuring. In a growing group of prostate cancer patients, it is not the final word. Research published in the July 2026 issue of The Journal of Nuclear Medicine shows that when a first PSMA PET scan finds nothing — yet a patient's PSA level keeps climbing — a second scan reveals previously hidden disease in more than half of those men.
The problem: a negative scan and a rising marker
After prostate cancer surgery or radiation, doctors watch the PSA — prostate-specific antigen — for signs of recurrence. When PSA rises, imaging is ordered. PSMA PET scans are the modern standard: a radioactive tracer binds to the prostate-specific membrane antigen on cancer cells, lighting up even tiny deposits that conventional CT or MRI can miss. But a first PSMA PET scan can still come back negative, usually because the recurrence is too small, too faint, or spread across too many sites to register at that moment.
The question is what to do next. The Ontario Registry for Recurrent Prostate Cancer study followed 210 men whose first scan was negative but whose PSA continued to rise. A second PSMA PET scan, performed months to years later, found disease in 56 percent of them — both local recurrences and distant metastases. In nearly half the cases the new information led to a change in treatment.
The hidden-recurring minority: 56% of patients with a negative first PSMA PET scan had disease detected on the second — including lesions that were too small or faint to appear the first time around.
Why waiting for a second scan works
PSMA PET is sensitive, but not infinitely so. A recurrence can be biologically present while remaining below the imaging threshold. Over time, as the disease grows, the signal crosses that threshold and becomes visible. The study found the biggest impact in men with oligometastatic disease — only a handful of metastatic sites — where a second scan's discovery can shift a patient from observation to targeted treatment of specific lesions.
What clinicians learned
The practical lesson is about timing and follow-up. A single negative scan should not close the case when PSA is rising. The data support a structured repeat-imaging strategy: reassess when PSA doubling time and clinical context suggest the first scan simply missed an early recurrence. For many patients this means a second scan at the right interval can find a disease burden small enough to treat effectively.
Knowledge takeaway: a second PSMA PET scan detected disease in 56% of men whose first scan was negative but PSA kept rising; nearly half of those patients had their treatment plan changed; the effect was greatest for men with a limited number of metastatic sites.