Response assessment of aggressive non-Hodgkin's lymphoma by integrated International Workshop Criteria and fluorine-18-fluorodeoxyglucose positron emission tomography

Purpose: To determine whether a response classification based on integration of fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) into the International Workshop Criteria (IWC) provides a more accurate response assessment than IWC alone in patients with non-Hodgkin's lymphoma (NHL). Patients and Methods: Fifty-four patients with aggressive NHL who underwent FDG-PET and computed tomography 1 to 16 weeks after four to eight cycles of chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone were assessed for complete response (CR), unconfirmed CR (CRu), partial response (PR), stable disease (SD), and progressive disease (PD) by the IWC and by integrated IWC and FDG-PET (IWC + PET). Progression-free survival (PFS) was also compared between IWC- and IWC + PET-assigned response designations. Results: By IWC, 17 patients had a CR, seven had a CRu, 19 had a PR, nine had SD, and two had PD. In comparison, by IWC + PET, 35 patients had a CR, 12 had a PR, six had SD, one had PD, and zero had a CRu. In separate multivariate models, PFS was significantly shorter in patients with PR than in those with a CR using IWC (hazard ratio [HR], 8.9; P = .021) or IWC + PET (HR, 29.7; P = .0003). However, when the two classifications were included in the same multivariate model, only IWC + PET was a statistically significant independent predictor for PFS (P = .008 v P = .72 for IWC). In addition, when patients with a PR by IWC and a CR by IWC + PET were compared with those with a CR by IWC and a CR by IWC + PET, there was no significant difference in PFS (HR, 1.6; P = .72), indicating that IWC + PET identified a subset of IWC-PR patients with a more favorable prognosis. Conclusion: Compared with IWC, the IWC + PET-based assessment provides a more accurate response classification in patients with aggressive NHL.