Table 1.
Definitions of Commonly Used Parameters in AA PET Studies
| Commonly Used Definitions | Studies Referenced | |
|---|---|---|
| PFS | Calculated as time from the beginning of BEV therapy to the first scan showing progression of disease. | Beppu et al., 20167 Beppu et al., 201927 Deuschl et al., 201726 Galldiks et al., 201311 George et al., 201823 Harris et al., 201228 Hutterer et al., 201113 Schwarzenberg et al., 201420 Wardak et al., 201430 |
| OS | Time from beginning BEV therapy until date of death or last follow-up. Note: Fleischmann et al., 2017 used post-recurrence survival, defined as time from initiation of radiation therapy with concomitant BEV until last follow-up or death. Hutterer et al., 2011 used a similar definition and termed it recurrent OS (rOS). Another variation reported by Galldiks et al., 2013 is total OS (tOS), defined as the standard OS or time from first diagnosis of tumor to death. |
Bashir et al., 201922 Deuschl et al., 201726 Fleischmann et al., 201725 Galldiks et al., 201311 George et al., 201823 Harris et al., 201228 Hutterer et al., 201113 Schwarzenberg et al., 201420 Wardak et al., 201430 |
| SUV | Calculated by adjusting activity concentration by the dose given and patient’s weight (injected activity/body weight). Note: Fleischmann et al., 2017 used early summation images to find ROIs with increased FET uptake, which aided in extraction of TACs for dynamic analysis. |
Beppu et al., 20167 Beppu et al., 201927 Deuschl et al., 201726 Fleischmann et al., 201725 Galldiks et al., 201311 Garcia et al., 201512 George et al., 201823 Harris et al., 201228 Humbert et al., 201929 Hutterer et al., 201113 Schwarzenberg et al., 201420 Wardak et al., 201430 |
| Normal, or nontumor SUV (SUVnormal) (alternatively known as tumor VOI) |
Calculated by outlining one or multiple ROIs of normal brain parenchyma in the contralateral hemisphere and determining the tracer uptake in this region. Note: George et al., 2018 used VOI to characterize tumor volume, however the definition is synonymous with SUV |
Bashir et al., 201922 Beppu et al., 20167 Beppu et al., 201927 Galldiks et al., 201311 Galldiks et al., 201824 George et al., 201823 Harris et al., 201228 Humbert et al., 201929 Hutterer et al., 201113 Schwarzenberg et al., 201420 |
| TBR or SUV of tumor/Normal- suvt/n | A comparison of the amount of amino acid tracer uptake (therefore metabolic activity) of the tumor (SUVtumor) to the apparently normal brain tissue (SUVnormal). Most studies used the threshold TBR greater than or equal to 1.6. Deuschl et al., 2017 used a threshold ratio of 1.3. Schwarzenberg et al., 2014 used TBRmax of 1.5. Fleischmann et al., 2017 used a TBRmax of 1.8. Harris et al., 2012 used a 95% confidence interval to determine which voxels had significant increases to calculate TBR, which they referred to as PRM. Note: Beppu et al, 2016 and 2019, and George et al., 2018, used the same measurement as above but used the terms SUVT/N and voxel-wise Spearman’s correlation coefficient, respectively. |
Bashir et al., 201922 Beppu et al., 20167 Beppu et al., 201927 Deuschl et al., 201726 Fleischmann et al., 201725 Galldiks et al., 201311 Galldiks et al., 201824 George et al., 201823 Harris et al., 201228 Schwarzenberg et al., 201420 |
| BTV or MTV | Volume of metabolically active tumor greater than the threshold determined by TBR. Most studies used the threshold TBR greater than or equal to 1.6. |
Bashir et al., 201922 Beppu et al., 20167 Beppu et al., 201927 Deuschl et al., 201726 Fleischmann et al., 201725 Galldiks et al., 201311 Galldiks et al., 201824 George et al., 201823 Harris et al., 201228 Humbert et al., 201929 Hutterer et al., 201113 Schwarzenberg et al., 201420 |
| Mean TBR (tbrmean) | The mean TBR is the average tracer uptake above the TBR threshold, therefore, it is the average BTV. | Beppu et al., 20167 Galldiks et al., 201311 Galldiks et al., 201824 Schwarzenberg et al., 201420 |
| Max TBR (TBRmax) | Calculated by the max SUV of the lesion (SUVlesion) divided by the mean SUV of normal brain parenchyma (SUVcontralateral normal brain tissue). Determined by images 5–40 min after injection of the tracer, depending on study methodology. | Beppu et al., 20167 Fleischmann et al., 201725 Galldiks et al., 201311 Galldiks et al., 201824 Schwarzenberg et al., 201420 |
| Tumor reduction | Threshold used to determine if the metabolically active tumor volume had significantly decreased. Most studies qualified this as tumor volume reduction of equal or greater than 45%. | Galldiks et al., 201311 Hutterer et al., 201113 |
| TAC) | Graph of the amount of tracer uptake in a specific tissue in relationship to the time since the injection of the tracer. | Fleischmann et al., 201725 Galldiks et al., 201311 Wardak et al., 201430 |
| TTP | Time between beginning of “dynamic acquisition” to the max SUV of the tumor. Alternatively described as the starting time frame plus half of the frame duration. | Fleischmann et al., 201725 Galldiks et al., 201311 |
BEV = bevacizumab; BTV = biological tumor volume; OS = overall survival; PFS, progression-free survival; MTV = metabolic tumor volume; PRM = parametric response maps; ROI = regions of interest; SUV = standardized uptake value; TAC = time activity curve; TBR = tumor-to-background ratio; TTP = time to peak; VOI = volume of interest.