Statistical analysis
The primary outcome, progression event-free survival (EFS), was defined
as the date from initiating therapy to recurrence or metastasis. In some
included studies, disease-free survival (DFS) or progression-free
survival (PFS) was obtained as the primary outcome, but they were all
redefined as EFS in this meta-analysis. The secondary outcome was overall
survival (OS), defined as the date from initiating therapy until death.
The effect sizes of the prognostic values of SUVmax,
SUVmean, MTV, and TLG were measured in terms of HR. An
HR greater than 1 implied worse survival for patients with a high
SUVmax, SUVmean, MTV, or TLG. The most
adjusted estimate of hazard ratio (HR) was extracted directly from each
study, if provided by the authors. Otherwise, the HR estimate and its
variance were extracted from Kaplan-Meier curves by Engauge Digitizer,
version 3.0 (http://digitizer.sourceforge.net). Heterogeneity was
assessed with the Q test and I 2 statistic, andP value less than 0.05 or I 2 values
higher than 50% indicated significant heterogeneity. The fixed-effects
model was used to estimate the cases with homogeneity and the
random-effects model was used for the cases with significant
heterogeneity. Publication bias of the studies was visually displayed by
the asymmetry of an inverted funnel plot, and quantitatively evaluated
by Egger’s tests with the P value less than 0.05 suggesting the
significant publication bias. Sensitivity analyses were conducted to
assess the stability of the meta-analysis results. All statistical
analysis was conducted with STATA 14.0 (STATA Corporation, College
Station, TX, USA) software.