qPET: Deauville With a Number
The same five scores, measured instead of eyeballed.
Deauville is read by eye, and the eye can be fooled. qPET measures the hottest residual lesion against the liver, giving a continuous number that sits on the familiar scale but separates patients the scale lumps together.
What it is
Formula
qPET = SUVpeak of the hottest residual lesion ÷ SUVmean of the liver
- Lesion: SUVpeak — the average of a small standardised cluster of the hottest voxels, not a single voxel.
- Liver: mean uptake in a large standardised volume of normal liver.
- Tool: semi-automatic; the mediastinum is not needed.
Why measure it
- Optical illusions: a lesion looks hotter against a cold background and cooler against a hot one.
- Response is a continuum: Deauville’s five boxes force a cut.
- Less observer-dependent, and trials can set the threshold for adequate response where they want it.
qPET ↔ Deauville
| qPET | Deauville equivalent | Meaning |
|---|---|---|
| < 0.95 | 1–2 | CMR |
| 0.95 – < 1.3 | 3 | CMR |
| 1.3 – 2.0 | 4 | Residual disease |
| > 2.0 | 5 | Residual disease |
CMR = complete metabolic response.
Remember
“Just under, a third over, double, triple.” 0.95 · 1.3 · 2 · 3 — each times the liver.
What the number adds
EuroNet-PHL-C1: 1,447 children with Hodgkin lymphoma, PET after two cycles. 5-year event-free survival:
| qPET | Event-free survival |
|---|---|
| < 1.3 | ~89% |
| 1.3–2 | 84% |
| 2–3 | 83% |
| > 3 | 48% |
The gain: Deauville 5 splits into 5A (2–3), which does as well as 4, and 5B (> 3), the truly high-risk group.
Pitfalls
- Evidence base: validated mainly in paediatric Hodgkin lymphoma; still a trial tool, not yet in Lugano.
- Needs a normal liver: hepatic involvement or diffuse liver disease breaks the denominator.
The visual scale it extends: Deauville scoring.
Take home
- qPET = hottest residual SUVpeak ÷ liver SUVmean — Deauville on a continuous scale.
- Cut-offs 0.95, 1.3 and 2 mark Deauville 3, 4 and 5. Below 1.3 is CMR.
- Its real gain is inside Deauville 5: qPET above 3 picks out the high-risk group.
Sources
- Hasenclever D, Kurch L, Mauz-Körholz C, et al. qPET – a quantitative extension of the Deauville scale to assess response in interim FDG-PET scans in lymphoma. Eur J Nucl Med Mol Imaging. 2014;41(7):1301-8.
- Kurch L, Landman-Parker J, Georgi TW, et al. Quantitative Deauville scoring to uncover prognostic information from 18F-FDG PET-based response assessment: data from the EuroNet-PHL-C1 trial. J Nucl Med. 2025;66(9):1331-7.
- Barrington SF, Kluge R. FDG PET for therapy monitoring in Hodgkin and non-Hodgkin lymphomas. Eur J Nucl Med Mol Imaging. 2017;44(Suppl 1):97-110.