Page 87 - 18F-FDG PET as biomarker in aggressive lymphoma; technical and clinical validation

PET/CT interobserver agreement in DLBCL
Figure 1. Example of discrepancy between reviewers’ assessment of mesenteric lymph nodes on, from left to right, axial attenuation-corrected PET, low-dose CT, and fused PET/CT images.
(A) Baseline 18F-FDG PET/CT with mesenteric bulky mass. (B) I-PET/CT after 4 cycles of R-CHOP14. One reviewer scored scan negatively (DS 1) and the other reviewer scored DS 4 for residual uptake in mesenteric mass. (C) EoT-PET/CT after 6 cycles of R-CHOP14. Both reviewers scored scan negatively (DS 1 and DS 2, respectively).
EoT-PET
Because in 10 EoT-PET scans one reviewer, and in 2 scans both, did not give a final conclusion, 457 scans were evaluable (Table 1). The median interval of EoT- PET scanning after the last chemotherapy cycle was 31 d (interquartile range, 22.5–48). The prevalence of positive EoT-PET scans was 17.5%. In 419 of 457 scans, the reviewers agreed on the final conclusion (negative or positive), yielding a percentage OA of 91.7% (95%CI, 89.0–94.3), a PA of 76.3% (95%CI, 66.3–86.2), and an NA of 95% (95%CI, 92.6–97.3).
Baseline 18F-FDG PET or PET/CT was available in 75% (n = 333 integrated PET/CT, and n = 10 PET stand-alone with a separate CT scan), and diagnostic CT was available in the remaining cases (n = 114). Percentage OA, NA, and PA did not significantly differ between these groups (percentage OA, 91% and 93.3%, P = 0.332; NA, 94.5% and 96.3%, P = 0.605; PA, 73.9% and 82.9%; P = 0.486). Percentage OA for R2-CHOP14 compared with RCHOP14 was 93.9 versus 89.4% (P = 0.082).
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