A New Scan Aims to Answer One of Brain Cancer's Hardest Questions

For people with glioblastoma and other gliomas, the weeks and months after surgery, radiation and chemotherapy bring a familiar fear. An MRI shows a new bright spot. Is the tumor back? Or is it swelling and scar tissue from treatment?

On MRI, the two can look nearly identical. Doctors call the treatment-related version "pseudoprogression" or, later on, "radiation necrosis." Getting the answer wrong in either direction matters. Mistaking treatment effects for tumor can mean stopping a treatment that's working or undergoing unnecessary surgery. Missing a true recurrence can delay the next treatment.

In September 2026, the FDA approved a new tool to help: floretyrosine F 18 (Pixclara), the first FDA-approved amino acid PET imaging agent for glioma.

How the scan works

Pixclara is a radioactive tracer, injected into a vein before a PET scan. It is a modified form of tyrosine, an amino acid. Glioma cells pull in amino acids far more than healthy brain tissue or treatment-damaged tissue does, using transporters on their surface called LAT1 and LAT2. So areas of active tumor tend to light up on the scan, while areas of treatment-related change usually don't.

The approach, known as FET-PET, isn't new. It has been used in Europe for years and was already recommended in the NCCN Guidelines. But until now, no FDA-approved version existed, which limited access for U.S. patients.

Who it's for

Pixclara is approved for adults and children as young as 1 month old with glioma, to help tell recurrent or progressing tumor apart from treatment-related change. It is meant to be used together with MRI and other tests, not instead of them.

How accurate is it?

No scan is perfect. Pooled research on FET-PET has found it correctly identifies true tumor progression about 88% of the time (sensitivity) and correctly identifies treatment-related change about 78% of the time (specificity). That's a meaningful improvement over MRI alone in these hard cases, but it still means some results will be wrong.

The prescribing information cautions that false positives and false negatives can happen, and that a negative scan does not rule out recurrence. Your care team will interpret the result alongside your symptoms, treatment history and other imaging.

Safety

In the 382 patients included in the safety data (371 adults and 11 children), side effects were uncommon. Headache was the most frequent. Nausea, injection-site reactions, fatigue and feeling unwell were each reported in fewer than 1 in 200 patients. As with any PET scan, it involves a small dose of radiation.

What this means for you

If you or a loved one has had treatment for a glioma and an MRI shows a change that's hard to read, an FET-PET scan may now be an option worth raising. It won't erase the uncertainty entirely, but it may shorten the painful stretch of "wait and rescan" and help your team make a more confident decision. Because the approval is new, availability at imaging centers and insurance coverage may take time to catch up.

Questions to ask your care team

• If my next MRI is unclear, would an FET-PET scan help us decide what to do?
• Is Pixclara available at this center, or would I need to go elsewhere?
• Will insurance cover it, and do you need to request prior authorization?
• If the PET and MRI disagree, how will we decide on next steps?

References

1. Targeted Oncology. "FDA Approves Pixclara, First FET-PET Agent for Glioma Imaging." September 2026.
2. CancerNetwork. "FDA Approves TLX101-Px for PET Imaging in Patients With Glioma." September 2026.
3. CancerNetwork. "FDA Receives NDA Resubmission for 18F-FET PET Imaging Agent in Recurrent Glioma." 2026.
4. National Brain Tumor Society. "FDA Approves First PET Imaging Agent for Glioma." Sept. 14, 2026.

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