Page 84 - 18F-FDG PET as biomarker in aggressive lymphoma; technical and clinical validation

Chapter 4
observer variation between the control and intervention arms. For comparison of the percentage OA, PA, and NA between groups, the χ2 test was used. A P value of less than 0.05 was considered statistically significant. Statistical analyses were performed using SPSS Statistics (IBM, version 20).
Results
Study Population
In total, 575 patients were eligible for the final analysis of the main trial [19]. I-PET and EoT-PET evaluation was performed in 534 and 517 patients, respectively (Supplemental Figs. 1 and 2; supplemental materials are available at http://jnm.snmjournals.org). For 7 patients, no PET data were received from the hospitals, 38 I-PET and 34 EoT-PET scans were performed on a stand- alone PET scanner, and 11 I-PET and 7 EoT-PET scans were not accessible in DICOM format or contained incomplete series.
I-PET
Table 1 summarizes the results of the interobserver agreement for I-PET with dichotomized DS. We obtained 465 evaluable scan results, because in 13 I-PET scans one of the reviewers did not provide a DS rating. The median time interval of I-PET scanning after the last chemotherapy cycle was 11 d (interquartile range, 9– 13 d). In 408 of 465 scans, the reviewers agreed on the final conclusion (negative or positive), yielding a percentage OA of 87.7% (95% confidence interval [95%CI], 84.7–90.8). The prevalence of positive I-PET scans was 23.3%. The NA, at 92% (95%CI, 89.1–95.0), was markedly higher than the PA, at 73.7% (95%CI, 65.0–82.5).
A baseline 18F-FDG PET or PET/CT scan was available in 77% (n = 349 integrated PET/CT scan and n = 8 PET stand-alone with a separate CT scan), and diagnostic CT in the remaining cases (n = 108). Percentage OA, NA, and PA were not statistically significant between these groups (percentage OA, 88% and 87%, P = 0.799; NA, 92% and 92%, P = 0.947; PA, 75.7% and 65%; P = 0.347). Percentage OA was similar in both treatment arms (P = 0.606).
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