Page 215 - 18F-FDG PET as biomarker in aggressive lymphoma; technical and clinical validation

Optimal timing and response criteria of Interim-PET in DLBCL
scores (DS) for the IAEA study, to assess extranodal involvement to determine the IPI score for the HOVON-84 study, and to measure the change in maximum standardized uptake value (∆SUVmax) for the Bologna, IAEA, HOVON-84, and SAKK studies [7-9,14]. Follow-up was updated for the GSTT15 and Bologna studies [7,10]. Patients were divided into 4 prognostic IPI score subgroups (low, low-intermediate, high-intermediate, and high) [4].
PET/CT review
All I-PET scans were reviewed according to the 5-point DS [5,6] by individual PETRA study groups. To harmonize DS5 scores between studies, we re-analyzed all DS5 patients, assigning DS5 if the lesional SUVmax exceeded 3 times the liver SUVmax and/or in the case of new lymphomatous lesions. We applied 2 different cutoffs for PET response assigning DS4-5, as recommended in international guidelines, and DS5 as PET-positive, respectively. Patients with a negative PET were considered to have a complete metabolic response. We also validated alternative criteria: ∆SUVmax between baseline and I-PET assessing response as ≥66% SUVmax reduction for I-PET scans after 1, 2, or 3 cycles [16], and ≥70% SUVmax reduction after 4 cycles of therapy [17], respectively.
Quality assessment
Two independent researchers ( J.J.E., C.N.B., or H.C.W.d.V.) rated the quality of included studies by scoring all relevant items with the Quality In Prognosis Studies (QUIPS) tool (ie, a risk of bias tool for prognosis studies) [18]. Quality was rated as high, low, or unclear risk of bias on the following aspects: study participation, study attrition, prognostic factor measurement, and outcome measurement. Differences in quality assessments were resolved by consensus.
Statistical analysis
A statistical plan was created before data were pooled and statistically analyzed. The primary end point of this study was 2-year PFS, defined as time from baseline PET to progression, relapse, or death as a result of any cause. Secondary end points were 2-year time to progression (TTP), defined as time from baseline PET to progression at which time patients dying within 2 years were censored, and 2-year OS, defined as time from baseline PET to death. Patients still alive were censored at date of last contact or the end of study period.
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