title: Identification of residual metabolic-active areas within individual NSCLC tumours using a pre-radiotherapy (18)Fluorodeoxyglucose-PET-CT scan.
abstract: OBJECTIVE
  Non-small cell lung cancer (NSCLC) tumours are mostly heterogeneous. We hypothesized that areas within the tumour with a high pre-radiation (18)F-deoxyglucose (FDG) uptake, could identify residual metabolic-active areas, ultimately enabling selective-boosting of tumour sub-volumes.
  
  
  METHODS
  Fifty-five patients with inoperable stage I-III NSCLC treated with chemo-radiation or with radiotherapy alone were included. For each patient one pre-radiotherapy and one post-radiotherapy FDG-PET-CT scans were available. Twenty-two patients showing persistent FDG uptake in the primary tumour after radiotherapy were analyzed. Overlap fractions (OFs) were calculated between standardized uptake value (SUV) threshold-based auto-delineations on the pre- and post-radiotherapy scan.
  
  
  RESULTS
  Patients with residual metabolic-active areas within the tumour had a significantly worse survival compared to individuals with a complete metabolic response (p=0.002). The residual metabolic-active areas within the tumour largely corresponded (OF>70%) with the 50%SUV high FDG uptake area of the pre-radiotherapy scan. The hotspot within the residual area (90%SUV) was completely within the GTV (OF=100%), and had a high overlap with the pre-radiotherapy 50%SUV threshold (OF>84%).
  
  
  CONCLUSIONS
  The location of residual metabolic-active areas within the primary tumour after therapy corresponded with the original high FDG uptake areas pre-radiotherapy. Therefore, a single pre-treatment FDG-PET-CT scan allows for the identification of residual metabolic-active areas.
authors.affiliation: Department of Radiation Oncology (MAASTRO), Grow-School for Oncology and Developmental Biology, Maastricht University, The Netherlands. Hugo.Aerts@maastro.nl
authors.forename: Hugo J W L
authors.initials: HJ
authors.lastname: Aerts
authors.forename: Angela A W
authors.initials: AA
authors.lastname: van Baardwijk
authors.forename: Steven F
authors.initials: SF
authors.lastname: Petit
authors.forename: Claudia
authors.initials: C
authors.lastname: Offermann
authors.forename: Judith van
authors.initials: Jv
authors.lastname: Loon
authors.forename: Ruud
authors.initials: R
authors.lastname: Houben
authors.forename: Anne-Marie C
authors.initials: AM
authors.lastname: Dingemans
authors.forename: Rinus
authors.initials: R
authors.lastname: Wanders
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Boersma
authors.forename: Jacques
authors.initials: J
authors.lastname: Borger
authors.forename: Gerben
authors.initials: G
authors.lastname: Bootsma
authors.forename: Wiel
authors.initials: W
authors.lastname: Geraedts
authors.forename: Cordula
authors.initials: C
authors.lastname: Pitz
authors.forename: Jean
authors.initials: J
authors.lastname: Simons
authors.forename: Bradly G
authors.initials: BG
authors.lastname: Wouters
authors.forename: Michel
authors.initials: M
authors.lastname: Oellers
authors.forename: Philippe
authors.initials: P
authors.lastname: Lambin
authors.forename: Geert
authors.initials: G
authors.lastname: Bosmans
authors.forename: Andre L A J
authors.initials: AL
authors.lastname: Dekker
authors.forename: Dirk
authors.initials: D
authors.lastname: De Ruysscher