What Your Deauville Score Means on a PET Report

The report landed in the portal at nine at night, the oncology appointment is next week, and the line that has your attention is a word and a number: "Deauville 2." Nobody said that number out loud at the infusion chair. It is sitting there next to your lymph nodes with no explanation attached, and there is a whole weekend before anyone will explain it.

The Short Answer

On a lymphoma PET report, the Deauville score is a 1 to 5 grade of how much radioactive tracer a treated site still takes up, compared against two reference points inside your own body: the blood pool in the middle of your chest and your liver. A 1 means no uptake at all and a 5 means markedly more than your liver. The dividing line runs at the liver, so scores at or below it are the reassuring half of the scale and scores above it are the half that gets looked at again. What counts as a good score also depends on whether this was a scan taken partway through treatment or the one after your last cycle.

The Line in Your Report

A treated lymphoma PET usually says it like this:

"Hepatic background" is your liver. "Mediastinal" means the middle of your chest, between the lungs. FDG is the radioactive sugar you were injected with, and cells that are burning energy fast take up more of it, which is why the American College of Radiology and RSNA patient site describes the tracer as collecting both in tumours and in regions of inflammation. So this sentence is saying that the nodes that lit up before treatment now take up less tracer than your own liver does, and that the one spot still glowing is a tonsil, which is a place tonsils glow anyway.

What Each Score Means

The five points were fixed at a lymphoma PET meeting in 2009 and are graded by eye rather than by measurement, a deliberate choice: visual comparison against your own organs is preferred to putting a number on the uptake, because your organs travel with you between scanners (Cancers, 2021).

Those are the definitions as they appear in the scoring table itself (Interim FDG-PET in Hodgkin's Lymphoma, 2011). The scale is not measuring your tumour, and it is not measuring how much disease is left. It answers one question about each treated site: is this spot brighter than your liver, and by how much.

The reason the reference organs are yours and not a fixed number is the same reason your report also carries SUV values that look inconsistent between hospitals. A different scanner, a different dose, a longer wait after the injection, all of these shift the raw brightness of the whole image, and they shift your liver along with everything else. Comparing a node to your own liver cancels most of that out.

The rest of the report can be read the same way, with each number placed next to what it was measured against rather than against a cutoff from the internet. That is the job our PET scan report reader does on the file you were handed.

Why the Same Scan Can Be Scored Differently

A 3 sits on the line: above your blood pool, at or below your liver. Whether that counts as a good result has changed inside a single clinical trial. The German HD18 trial originally treated a Deauville 3 or higher as a positive scan, and then moved the cutoff to 4 or higher partway through, while in patients treated with the ABVD regimen a 3 at the end of chemotherapy was taken as a complete metabolic response (Cancers, 2021).

Same image, same score, opposite reading, depending on the protocol your team follows and what you were treated with. If your report says 3, "what does 3 mean here" is a real question with a real answer, and it is not a question you can settle by reading about the scale in general.

An Interim Scan and a Final Scan Are Not Read the Same Way

The timing matters more than most patients are told. A scan taken after two cycles of chemotherapy, often written as PET2, is described by the National Cancer Institute as the best single predictor of treatment failure in Hodgkin lymphoma. That is what makes it worth doing partway through.

It is also where the false alarms cluster. The NCI notes that in limited-stage disease, positive interim scans are frequently false, because the underlying chance of relapse is low to begin with. And a clean interim scan is not a guarantee either: in advanced-stage disease, up to 15% of patients relapse despite a negative PET2.

For the scan after treatment finishes, the asymmetry is the useful part. Post-chemotherapy PET in Hodgkin lymphoma has a negative predictive value between 94% and 86%, while its positive predictive value runs between 40% and 25% (Cancers, 2021). A scan that says nothing is lit up is usually right. A scan that says something is lit up is wrong more often than it is right, which is why a positive result is followed by more tests rather than by a decision.

What a 4 or a 5 Does Not Mean

The biopsy numbers are the clearest way to see this. In a study of 169 patients, the 43 whose restaging scans came back positive went on to imaging-guided biopsy. Tissue confirmed lymphoma in 100% of the cases scored Deauville 5, and in 12.5% of the cases scored Deauville 4 (Cancers, 2021).

Seven out of eight Deauville 4 scans in that group were something else.

A separate group looked at 102 PET-CTs in diffuse large B-cell lymphoma, mostly interim scans, of which 36 were positive. When those patients were biopsied, 74% of the biopsies came back negative, and 20 of those negative biopsies were taken from patients whose PET-CT had been read as positive (Tokola et al., 2021). The authors' conclusion was that in this disease, tissue should be obtained before a treatment decision is made on a positive scan alone.

What the something else usually is, is inflammation. Faint leftover uptake at a treated site is generally taken to represent an inflammatory reaction following chemotherapy, with FDG collecting there nonspecifically (Interim FDG-PET in Hodgkin's Lymphoma, 2011). Treatment damages tissue, damaged tissue recruits immune cells, and immune cells burn sugar. The tracer cannot tell the difference between a cell fighting lymphoma and a lymphoma cell.

Questions to Ask at Your Appointment

• Was this an interim scan or an end-of-treatment scan, and which cutoff does my protocol use for a positive result?
• Which sites were scored, and how do those scores compare with my baseline scan before treatment?
• If a site scored 4 or 5, is it in the same place as my original disease, or somewhere new?
• How long was it between my last cycle and this scan?
• What would have to be true for a biopsy to be the next step rather than another scan?

Frequently Asked Questions

Is a Deauville 2 the same as remission?

A Deauville 2 means the treated sites now take up less tracer than your blood pool, which radiologists read as a complete metabolic response. Remission is a word your oncologist uses after putting that scan next to your bloodwork, your symptoms and where you are in treatment. The scan is one input to it, not the word itself.

Does a Deauville 4 mean the lymphoma is still there?

Often it does not. In a study of 169 patients where the positive restaging scans were biopsied, tissue confirmed lymphoma in 100% of the Deauville 5 cases but only 12.5% of the Deauville 4 cases. A 4 is the score that most often turns out to be something other than disease.

Why is Deauville 3 treated differently from the other scores?

A 3 means uptake above your blood pool but at or below your liver, which sits exactly on the dividing line. Some treatment protocols count it as a positive scan and others count it as a complete response, so the same picture can be read either way depending on which protocol your team follows.

My score got worse between two scans. What does that mean?

A score rising from one scan to the next is read against when each scan was taken, because a mid-treatment scan and an end-of-treatment scan are interpreted on different terms. Ask which of the two this was and whether the reference organs were the liver and blood pool both times.

Can inflammation from chemotherapy push the score up?

Yes, and it is the usual explanation for faint leftover uptake. FDG collects in inflamed tissue as well as in tumour, and treated tissue is inflamed tissue, which is why timing between the last cycle and the scan matters to the people reading it.

Related Articles

• PET Scan Report Explained: What Uptake Means covers SUV values, hypermetabolic sites and the rest of the report around the Deauville line.
• What Does Impression Mean on a Radiology Report explains which section of the report carries the radiologist's actual conclusion.
• PSMA PET-CT for Prostate Cancer Explained walks through a different PET scoring system on the same kind of scan.

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Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for diagnosis and treatment decisions.