Correlation analysis of [¹⁸F]fluorodeoxyglucose and [¹⁸F]fluoroazomycin arabinoside uptake distributions in lung tumours during radiation therapy

Abstract

Background: PET-guided dose painting (DP) aims to target radioresistant tumour regions in order to improve radiotherapy (RT) outcome. Besides the well-known [¹⁸F]fluorodeoxyglucose (FDG), the hypoxia positron emission tomography (PET) tracer [¹⁸F]fluoroazomycin arabinoside (FAZA) could provide further useful information to guide the radiation dose prescription. In this study, we compare the spatial distributions of FDG and FAZA PET uptakes in lung tumours.

Material and methods: Fourteen patients with unresectable lung cancer underwent FDG and FAZA 4D-PET/CT on consecutive days at three time-points: prior to RT (pre), and during the second (w2), and the third (w3) weeks of RT. All PET/CT were reconstructed in their time-averaged midposition (MidP). The metabolic tumour volume (MTV: FDG standardised uptake value (SUV) > 50% SUV_max), and the hypoxic volume (HV: FAZA SUV > 1.4) were delineated within the gross tumour volume (GTV_CT). FDG and FAZA intratumoral PET uptake distributions were subsequently pairwise compared, using both volume-, and voxel-based analyses.

Results: Volume-based analysis showed large overlap between MTV and HV: median overlapping fraction was 0.90, 0.94 and 0.94, at the pre, w2 and w3 time-points, respectively. Voxel-wise analysis between FDG and FAZA intratumoral PET uptake distributions showed high correlation: median Spearman’s rank correlation coefficient was 0.76, 0.77 and 0.76, at the pre, w2 and w3 time-points, respectively. Interestingly, tumours with high FAZA uptake tended to show more similarity between FDG and FAZA intratumoral uptake distributions than those with low FAZA uptake.

Conclusions: In unresectable lung carcinomas, FDG and FAZA PET uptake distributions displayed unexpectedly strong similarity, despite the distinct pathways targeted by these tracers. Hypoxia PET with FAZA brought very little added value over FDG from the perspective of DP in this population.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional committee on human experimentation and with the Helsinki declaration of 1975, as revised in 1983.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Disclosure statement

None to declare.

Additional information

Funding

Dario Di Perri is a doctoral researcher funded by ‘Fonds de la Recherche Scientifique – FNRS – Télévie’ (grant no. 7.4572.13F). Xavier Geets is a post-doctoral clinician-researcher, partly funded by ‘Fondation Contre le Cancer’ (grant no. 2014-086). John A. Lee is a research associate with ‘Fonds de la Recherche Scientifique – FNRS’.