Table 2.

Role for PET-CT in staging and restaging patients with DLBCL and FL

DLBCL	FL
Baseline PET used for:
Risk stratification	Risk stratification
NCCN-IPI using PET discriminates patients with very good prognosis from patients at high risk of treatment failure, mostly elderly patients unsuitable for salvage treatments for whom testing with novel agents may be appropriate	PET-CT upstages patients compared to CT; effect on outcomes not known
Parameters including number of extranodal sites and metabolic tumour burden, also combined with early response are promising predictors of prognosis.
Staging including bone marrow assessment	Staging
Can replace bone marrow biopsy in selected cases	To assess suitability for local (RT) or systemic treatment low sensitivity for bone marrow assessment; bone marrow biopsy required
Mapping initial disease sites for accurate response assessment	Mapping initial disease sites for accurate response assessment
Differentiating lymphomatous involvement from other causes for increased FDG uptake, e.g. infection, inflammation, bone marrow hyperplasia	Differentiating lymphomatous involvement from other causes for increased FDG uptake, e.g. infection, inflammation, bone marrow hyperplasia
Interim PET used for:
Prognosis	Prognostic but no current role
Early CMR has excellent prognosis and usually predicts CMR at end of treatment; such patients do not require end-of-treatment scans.
Patients with a positive interim PET and other high risk features, e.g. poor-risk IPI, may require close monitoring during treatment as they have higher risk of refractory disease and relapse.
PET is a more appropriate test for interim imaging assessment than CT.
Excluding disease progression on treatment
But should not be used to change standard treatment unless clear evidence of progression. To date, no evidence exists that response adaptation at interim on the basis of positive PET improves patient outcomes and risks over-treating many patients.
End of treatment PET used for:
Remission assessment	Remission assessment
Using Deauville criteria. Patients with end-of-treatment Deauville scores 4 and 5 should be considered for further treatment with biopsy confirmation wherever feasible but particularly if salvage treatment ± ASCT is being considered.	After induction treatment with R-CHOP(-like) chemotherapy using Deauville criteria. Patients with end-of-treatment Deauville scores 4 and 5 have worse outcomes than patients achieving CMR and may be suitable for testing of response-adapted strategies.
Decision making as to suitability for ASCT following high-dose chemotherapy	Early data suggest may be predictive of outcomes after following high-dose chemotherapy prior to ASCT.
In preference to CT