Metabolic control probability in tumour subvolumes or how to guide tumour dose redistribution in non-small cell lung cancer (NSCLC): An exploratory clinical study

PurposeTo characterize the relationship between pre-radiotherapy 18Fluorodeoxyglucose (FDG) uptake in a tumour voxel, radiation dose and the probability to achieve metabolic control in the tumour voxel after radiotherapy.Materials and methodsThirty-nine patients with inoperable stage I-III non-small cell lung cancer, treated with radiotherapy (RT) alone or sequential chemo radiation were analysed retrospectively. Twenty-two showed metabolic active areas in the tumour 3 months post-radiotherapy, which is known to be a surrogate for persistent local tumour failure and worse survival. Pre- and post-RT FDG-PET-CT scans were registered and the metabolic active zones within the tumour after RT were projected on the pre-RT scan. Multi-level logistic regression was performed to determine the relation between the FDG uptake if a voxel pre-RT and its metabolic state after RT.ResultsThe probability that a voxel is metabolically controlled (mVCP), decreased significantly with increasing FDG uptake in a voxel (SUV) (OR = 0.72), increasing tumour volume (20 cm3) (OR = 0.89) and increasing dose (Gy) (OR = 0.99). Inter-patient differences in mVCP were substantial.ConclusionA methodology was presented to derive relationships between FDG uptake, dose and metabolic control. Although no strong dose effect relation was demonstrated, mVCP decreased with increasing FDG uptake and tumour volume.