CT-based versus FDG-PET/CT-based NCCN international prognostic index risk stratification in DLBCL
Hugo J A Adams1, John M H de Klerk1, Rob Fijnheer1
1From the Departments of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, and the Departments of Nuclear Medicine, Hematology, and Pathology, Meander Medical Center, Amersfoort, The Netherlands.
Background:
This study compared CT-based and (18)F-fluoro-2-deoxy-D-glucose PET/CT (FDG-PET/CT)-based NCCN International Prognostic Index (NCCN-IPI) risk stratification in newly diagnosed diffuse large B-cell lymphoma (DLBCL).
Materials And Methods:
This retrospective study included 57 patients with newly diagnosed DLBCL who had undergone both (oral and intravenous contrast-enhanced full-dose) diagnostic CT and FDG-PET/CT. Diagnostic CT only and FDG-PET/CT were evaluated separately, and corresponding NCCN-IPI scores for the 2 datasets (NCCN-IPICT and NCCN-IPIPET/CT) were calculated. Percentages of agreement and weighted k statistic between NCCN-IPICT and NCCN-IPIPET/CT scoring with regard to the formation of low-, low-intermediate-, high-intermediate-, and high-risk groups were calculated.
Results:
In 47 of 57 patients (82.5%; 95% CI, 70.4-90.4), diagnostic CT alone was in agreement with FDG-PET/CT with regard to the formation of low-, low-intermediate-, high-intermediate-, and high-risk NCCN-IPI groups, but not in the remaining 10 patients (17.5%; 95% CI, 9.6%-29.6%). All NCCN-IPI disagreements between diagnostic CT and FDG-PET/CT were from the detection of additional lesions by the latter, most of them being bone marrow lesions. Agreement between NCCN-IPICT and NCCN-IPIPET/CT with regard to the formation of low-, low-intermediate-, high-intermediate-, and high-risk groups was considered good (k=0.771).
Conclusions:
Although agreement between NCCN-IPICT and NCCN-IPIPET/CT risk stratification is generally good, FDG-PET/CT results in higher NCCN-IPI risk stratifications in a non-negligible proportion of patients. Future studies should investigate the prognostic implications of these imaging-based differences in NCCN-IPI scoring.