Preliminary assessment of dynamic contrast-enhanced CT implementation in pretreatment FDG-PET/CT for outcome prediction in head and neck tumors

Background: Recently published data show some controversy concerning the impact of [18F]-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in predicting head and neck tumors (HNT) outcome. Assessment of tumor blood supply parameters using dynamic contrast-enhanced CT (DCE-CT) may deliver additional information concerning this important question. Purpose: To evaluate the contribution of DCE-CT implemented in pretherapeutic FDG-PET/CT protocol for prognosis prediction in patients with HNT. Material and Methods: Ten consecutive patients (median age 50 years, range 47-74 years) with histologically proven HNT underwent FDG-PET/CT with DCE-CT before treatment. FDG uptake was measured by maximum standardized uptake value (SUV(max)). Relative tumor blood volume (rTBV) was determined from DCE-CT using Patlak analysis. Intratumoral heterogeneity was assessed by means of lacunarity analysis. Obtained values were compared with time-to-progression and overall survival. PET and DCE-CT images were compared on a pixel-by-pixel basis using Pearson coefficient of correlation. Results: Three patients with lower FDG uptake (SUV(max) : 8 +/- 1) and five patients with higher FDG uptake (SUV(max) : 15 +/- 4, P = 0.004) were free of local recurrence for 24 months. Two groups of patients with significantly differing lower (group A: 0.37 +/- 0.02, n = 6) and higher (group B: 0.52 +/- 0.01, n = 4; P < 0.01), tumor heterogeneity (lacunarity) were identified. Corresponding mean rTBV was higher in group A (9.6 +/- 1.8 ml/100 ml) than in group B (6.2 +/- 0.6 ml/100 ml). All six patients with homogeneous tumor blood supply (lower lacunarity) and higher rTBV were free of local recurrence during 24 months, while two of four patients with heterogeneous tumor blood supply (higher lacunarity) and lower rTBV died during follow-up due to tumor relapse. A weak correlation between FDG-PET and DCE-CT rTBV was observed (R(2)=0.1). Conclusion: FDG-PET/CT and DCT-CT are complementary methods for surveillance assessment in patients with HNT. Implementation of DCE-CT in the pretreatment FDG-PET/CT protocol may improve tumor outcome prediction.