Residual metabolic tumor activity after chemo-radiotherapy is mainly located in initially high FDG uptake areas in rectal cancer

Jorgen van den Bogaard, Marco H. M. Janssen*, Geert O. Janssens, Jeroen Buijsen, Brigitte Reniers, Philippe Lambin, Guido Lammering, Michel C. Ollers

*Corresponding author for this work

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Recent literature suggests that tumor cells and areas within tumors with a high initial FDG uptake might be more resistant to (chemo)radiotherapy ((C)RT). This study was undertaken to test this hypothesis in rectal cancer using rigid and non-rigid image registration.Twenty-eight patients, diagnosed with locally advanced rectal cancer and referred for pre-operative treatment with CRT were included in this study. All patients underwent FDG-PET-CT imaging prior to and after CRT. Rigid and non-rigid image registration was performed to compensate organ deformations between the pre- and post-treatment PET-CT scans. The tumor was contoured on both PET-scans using SUV iso-contouring based on the SBR-method. The voxels with residual increased FDG uptake were studied and correlated to their pre-treatment FDG uptake level. Two SUV-volume-histograms were made based on the pre-treatment PET-data, one for the voxels within the pre-treatment tumor PET-based iso-contour and one for the voxels within the PET-based iso-contour of the residual tumor non-rigidly registered onto the pre-treatment scan.For the voxels with a pre-treatment FDG uptake of >50% of SUV(max), 70.6?5.6% of the voxels were still metabolic active in the residual tumor, whereas for voxels with an FDG uptake of
Original languageEnglish
Pages (from-to)137-141
JournalRadiotherapy and Oncology
Issue number2
Publication statusPublished - May 2011


  • Non-rigid image registration
  • Rectal cancer
  • FDG uptake
  • Residual disease
  • Morphons

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