Scan time-normalized tumor to blood standard uptake ratio (SUR) in pretherapeutic FDG PET is superior to SUV as a prognostic factor in patients with esophageal carcinoma

Ziel/Aim:

Tumor SUV is widely used for quantitative assessment of tumor metabolism in FDG PET and its potential for therapy outcome prediction in various cancer diseases has been investigated in many publications. However, the SUV approach has well known limitations compromising its ability to act as a surrogate parameter of glucose consumption. Recently, we have shown that SUR overcomes most of these limitations as long as FDG kinetics in the target structure can be considered irreversible [1,2]. The aim of this work was to compare the prognostic value of SUR and SUV in patients with esophageal carcinoma.
Methodik/Methods:
FDG-PET/CT was performed in 103 consecutive patients ((63+/-11)y, 89 males) with newly diagnosed esophageal cancer prior to definitive radiochemotherapy. In the PET images the metabolic active volume (MTV) of the primary tumor was delineated with an adaptive threshold method. The blood SUV was determined by manually delineating the aorta in the low dose CT. SUR values were computed as ratio of tumor SUV and blood SUV. SUR values were
scan-time-normalized to 60 min p.i. as described in [2]. Kaplan-Meier analysis and univariate Cox regression with respect to overall survival (OS), locoregional control (LRC), and distant-metastases-free survival (DM) was performed
for SUV_max, SUR_max and clinically relevant parameters. Additionally, a multivariate Cox regression including clinical parameters, which were univariate significant, as confounding factors was performed.
Ergebnisse/Results:
Both, SUV_max and SUR_max, were prognostic factors for OS and DM, but not for LRC. With respect to OS a univariate Cox regression showed a slightly increased hazard ratio (HR) for SUR_max (HR=2.2, p=0.003) compared to SUV_max (HR=1.8, p=0.01). With respect to DM HR of SUR_max was notably larger than HR of SUV_max (HR=6.5, p=0.01 compared to 2.8, p=0.044). Moreover, in multivariate Cox regression only SUR was an independent prognostic factor for OS and for DM the prognostic value of SUR was notably higher than of SUV.
Schlussfolgerungen/Conclusions:
Our results indicate that blood- and time-normalization increases the prognostic value of lesion uptake in pretherapeutic FDG PET of patients with esophageal carcinoma. More comprehensive investigations are necessary to confirm these results.
Literatur/References:
[1] van den Hoff et al, EJNMMI Res 2013, 3:77.[2] van den Hoff et al, EJNMMI Res 2014, 4:18.