Which statement about the role of PET-CT in lymphoma response assessment is true?

• A. PET-CT is central to response assessment in Lugano-based staging
• B. CT alone is always sufficient for response assessment
• C. MRI is preferred over PET-CT for nodal response
• D. Ultrasound is the primary modality for response assessment

Answer: (A)

Understanding how lymphoma treatment response is assessed hinges on combining metabolic information with anatomical detail. In FDG-avid lymphomas, the Lugano response framework relies on PET-CT as the primary tool for evaluating treatment response and restaging. This means we look at how much metabolic activity remains in previously involved sites after therapy, often using the Deauville five-point scale to categorize responses from complete metabolic response to progression. PET-CT gives a fuller picture than anatomy alone because a mass that has shrunk on CT may still harbor active disease, while a persistently active lesion signals residual disease even if size has decreased.

CT can show size changes but cannot reliably distinguish viable tumor from scar tissue or inflammation post-treatment, so CT alone isn’t always sufficient. MRI has strong soft-tissue contrast but for nodal response it doesn’t provide the same whole-body metabolic information or practicality as PET-CT. Ultrasound is limited to accessible superficial nodes and doesn’t survey the full set of nodal and extranodal sites that PET-CT can assess, nor does it give metabolic data. Therefore, PET-CT’s role as the central imaging modality in Lugano-based response assessment best reflects current practice.