Asphericity of pretherapeutic FDG uptake predicts outcome in NSCLC

Ziel/Aim:

FDG-PET/CT has become the standard for staging of local tumor extent, mediastinal lymph node involvement and distant metastatic disease in patients with non-small-cell lung cancer (NSCLC). However, its role for prognosis is less clear. The aim of the present study was to evaluate the prognostic value of a novel quantitative measure for the spatial heterogeneity of FDG uptake, the asphericity (ASP).

Methodik/Methods:

FDG-PET/CT had been performed in 47 patients (65.1±8.8y, 38 males) with newly diagnosed NSCLC prior to treatment. PET images of the primary tumor were segmented using the ROVER 3D segmentation tool based on thresholding at the volume-reproducible intensity threshold after subtraction of local background. The ASP defined as the deviation of the tumor's shape from sphere symmetry was implemented in ROVER. Kaplan-Meier analysis with respect to overall (OS) and progression-free survival (PFS) was performed for localization (central vs. peripheral), SUVmax, metabolically active tumor volume (MTV), total lesion glycolysis (MTV*SUVmean) and ASP. OS and PFS curves were separated by the median value and compared by log-rank tests.

Ergebnisse/Results:

32 patients experienced tumor progression or recurrence after a median interval of 6.2 (range, 0.4-26.7) months. 19 of these patients died during a median follow-up of 8.7 (0.4-26.7) months. ASP was the only prognostic factor for PFS (p=0.01): the probability of 1-year PFS decreased from 69 % in the patients with low ASP to 37 % in the patients with high ASP. Furthermore, there was a tendency towards longer OS in case of small vs large ASP (p=0.06, 1-year-OS 81% vs 51%). The localization of the tumor was a strong predictor for OS (p=0.004, 1-year OS 78% vs 25% for peripheral vs central localization), but not for PFS (p=0.12).

Schlussfolgerungen/Conclusions:

The novel parameter asphericity of the pretherapeutic FDG-uptake provides more power for the prediction of PFS in NCSLC than conventional quantitative measures including SUVmax, MTV and glycolytic tumor volume.