Deauville five-point scale for PET

The Deauville five-point scale (also called the 5-point scale, 5PS) grades FDG uptake in each lymphoma lesion visually against two internal reference tissues: the mediastinal blood pool and the liver. Score 1 is no uptake above background; 2 is uptake at or below the mediastinal blood pool; 3 is uptake above the mediastinum but at or below the liver; 4 is uptake moderately higher than liver; 5 is uptake markedly higher than liver and/or new lesions. An additional X denotes new uptake felt unlikely to be lymphoma. Proposed in 2009 and incorporated into the 2014 Lugano classification for staging and response assessment, it is now the standard scale for FDG-avid nodal lymphomas including Hodgkin lymphoma and most non-Hodgkin subtypes.

Under Lugano, a complete metabolic response is a Deauville score of 1, 2 or 3 (with or without a residual mass) and no marrow involvement; a partial metabolic response is score 4 or 5 with reduced uptake from baseline; no metabolic response (stable disease) is score 4 or 5 unchanged; progressive metabolic disease is score 4 or 5 with increasing uptake or new FDG-avid lesions. Score 3 is generally treated as a good-prognosis complete response, except in de-escalation trials, where some protocols treat score 3 as an inadequate interim response to avoid undertreatment.

The scale's simplicity and reproducibility drove its adoption in trials such as RATHL, which used interim PET response to de-escalate or intensify treatment in advanced Hodgkin lymphoma. A residual mass greater than 2 cm alongside a Deauville 1-2 result at end of treatment has been associated with a higher relapse risk in diffuse large B-cell lymphoma in some series, illustrating that the scale is read alongside anatomic findings rather than in isolation.