Table 4. Revised Criteria for Response Assessment in Lymphoma based on FDG PET/CT imaging.
| Response category | FDG-PET/CT-Based Response Criteria |
|---|---|
| Complete metabolic response (CMR) | Nodes and extralymphatic sites: Score 1, 2, or 3* with or without a residual mass on 5PS No new lesions In the setting of previous organ enlargement, regress to normal No FDG-uptake in bone marrow |
| Partial metabolic response (PMR) | Nodes and extralymphatic sites: Score 4 or 5 with reduced uptake compared with baseline and residual mass(es) of any size
No new lesions Residual uptake higher than uptake in normal bone marrow but reduced compared with baseline (diffuse uptake compatible with reactive changes from chemotherapy or G-CGF allowed). If there are persistent focal changes in the marrow in the context of a nodal response, consideration should be given to further evaluation with MRI or biopsy or an interval scan |
| Stable Disease (SD) or No metabolic response | Nodes and extralymphatic sites: Score 4 or 5 with no significant change in FDG uptake from baseline at interim or end of treatment No new lesions No changes in bone marrow from baseline |
| Progressive Disease (PD) | Nodes and extralymphatic sites: Score 4 or 5 with an increase in intensity of uptake from baseline and/or New FDG-avid extranodal foci consistent with lymphoma at interim or end-of-treatment assessment New FDG-avidlesions consistent with lymphoma, not attributed to other condictions (eg, infection, inflammation). If uncertain regarding etiology of new lesions, biopsy or interval scan may be considered New or recurrent FDG-avid foci in bone marrow |
Abreviations: 5PS, point scale from DeauvilleCretaria: 1, No increased FDG ptake above background; 2, FDG uptake ≤ mediastinum; 3, FDG uptake > mediastinum but ≤ liver; 4, FDG uptake moderately higher than liver; 5, FDG uptake markedly higher than liver and/or new lesions; X, New areas of FDG uptake unlikely to be related to lymphoma
The addition of score 3 for interim analysis during therapy accounts for sites with activation during chemotherapy such as Waldeyer's ring, spleen or bone marrow. In those cases, a score of 3 indicates a good prognosis with standard treatment, especially if at the time of an interim scan. However, in trials exploring treatment de-escalation, a score 3 should be considered as an inadequate response to avoid under treatment
It is known that in Waldeyer's ring or extranodal sites with high physiologic FDG-uptake (eg, GI tract, liver, bone marrow) or with reactive activation within the spleen or bone marrow (eg, with chemotherapy or G-CSF), uptake may be greater than the mediastinum. In this circumstance, CMR may be inferred if uptake at sites of initial involvement is no greater than surrounding normal tissue, even if the tissue has high physiologic uptake