Metabolic control probability in tumour subvolumes or how to guide tumour dose redistribution in non-small cell lung cancer (NSCLC): an exploratory clinical study.
OBJECTIVE
To characterize the relationship between pre-radiotherapy (18)Fluorodeoxyglucose (FDG) uptake in a tumour voxel, radiation dose and the probability to achieve metabolic control in the tumour voxel after radiotherapy.


METHODS
Thirty-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.


RESULTS
The 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 cm(3)) (OR=0.89) and increasing dose (Gy) (OR=0.99). Inter-patient differences in mVCP were substantial.


CONCLUSIONS
A 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.
Petit
Steven F
SF
Department of Radiation Oncology (Maastro Clinic), Maastricht University Medical Center (MUMC+), Maastricht, The Netherlands. steven.petit@maastro.nl
Aerts
Hugo J W L
HJ
van Loon
Judith G M
JG
Offermann
Claudia
C
Houben
Ruud
R
Winkens
Bjorn
B
Ollers
Michel C
MC
Lambin
Philippe
P
De Ruysscher
Dirk
D
Dekker
André L A J
AL