Table 2. Revised Criteria for Response Assessment in Lymphoma based on CT imaging.

Response category	CT-Based Response Criteria
Complete Remission (CR)	Target nodes/nodal masses must regress to ≤ 1.5 cm in LDi. It includes the presence of residual symptoms but no detectable disease by imaging No extralymphatic sites of disease No nonmeasured lesions No new lesions In the setting of previous organ enlargement, regress to normal Bone marrow normal by morphology; if indeterminate, IHC negative
Partial Remission (PR)	≥ 50% decrease in SPD of up to 6 measurable target measurable nodes and extranodal sites When a lesion is too small to measure on CT, assign 5 × 5 mm as the default value When no longer visible, 0 × 0 mm When a node is > 5 × 5 mm, but smaller than normal, use actual measurement for calculation No new lesions In the setting of previous nonmeasured lesions, regress to normal, no increase Spleen must have regressed by > 50% in length beyond normal
Stable Disease (SD)	< 50% decrease from baseline in SPD of up to 6 dominant, measurable nodes and extranodal sites No increase in nonmeasurable lesions or organ enlargement consistent with progression No new lesions
Progressive Disease (PD)	An individual node/lesion must be abnormal with LDi > 1.5 cm, and increase by ≥50% from PPD nadir, and an increase in LDi or SDi from nadir of 0.5 cm for lesions ≤ 2 cm or 1 cm for lesions > 2 cm New or clear progression of preexisting nonmeasured lesions Presence of new lesions Regrowth of previously resolved lesions A new node > 1.5 cm in any axis A new extranodal site > 1 cm in any axis; if < 1 cm, its presence must be unequivocal and must be attributable to lymphoma Assessable disease of any size unequivocal to lymphoma In the setting of splenomegaly, the splenic length must increase by > 50% of the extent of its prior increase beyond baseline (e.g., a 15 cm spleen must increase to > 16 cm). If no prior splenomegaly, must increase by at least 2 cm from baseline New or recurrent splenomegaly New or recurrent bone marrow involvement

Abreviations: LDi, longest diameter of the lesion; SDi, shortest axis perpendicular to the LDi; SPD, sum of the product of the perpendicular diameters for multiple lesions; PPD, cross product of the LDi and perpendicular diameter; IHC, immunohistochemistry

Measured dominant lesions: Up to six of the largest dominant nodes, nodal masses, and extranodal lesions selected to be clearly measurable in two diameters, the longest diameter (LDi) and the shortest perpendicular to the LDi diameter (SDi). Nodes should preferably be from disparate regions of the body and should include, where applicable, mediastinal and retroperitoneal areas

- Measurable node: LDi > 1.5 cm

- Measurable extranodal disease: LDi > 1 cm

Non-nodal lesions: include those in solid organs (eg, liver, spleen, kidneys, lungs), GI involvement, cutaneous lesions, or those noted on palpation

Nonmeasured lesions: any disease not selected as measured, dominant disease and truly assessable disease should be considered not measured. These sites include any nodes, nodal masses, and extranodal sites not selected as dominant or measurable or that do not meet the requirements for measurability but are still considered abnormal, as well as truly assessable disease, which is any site of suspected disease that would be difficult to follow quantitatively with measurement, including pleural effusions, ascites, bone lesions, leptomeningeal disease, abdominal masses, and other lesions that can not be confirmed and followed by imaging