Defining Radiotherapy Target Volumes Using 18F-Fluoro-Deoxy-Glucose Positron Emission Tomography/Computed Tomography: Still a Pandora’s Box?: In Regard to Devic et al. ( Int J Radiat Oncol Biol Phys 2010)

Abstract

To the Editor: We read with interest the article by Devic et al.( 1 Devic S. Tomic N. Faria S. et al. Defining radiotherapy target volumes using 18F-fluoro-deoxy-glucose positron emission tomography/computed tomography: Still a Pandora’s box?. Int J Radiat Oncol Biol Phys. 2010; (In Press) Google Scholar ) investigating the use of fixed thresholds to define non–small-cell lung carcinoma tumor positron emission tomography (PET) volumes exhibiting heterogeneous uptake. They found no correlation between the computed tomography–based and the PET-based volumes, and they associated the observed variations with intrinsic properties of PET acquisition rather than the segmentation choice. They also concluded that PET-based volumes should not be used for radiotherapy dose painting/boosting. Several studies recently dealt with similar issues considering fixed threshold to determine tumor metabolic volumes, showing large variability in the threshold values ( 2 Han D. Yu J. Yu Y. et al. Comparison of 18F-fluorothymidine and 18F-fluorodeoxyglucose PET/CT in delineating gross tumor volume by optimal threshold in patients with squamous cell carcinoma of thoracic esophagus. Int J Radiat Oncol Biol Phys. 2010; 76: 1235-1241 Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar , 3 Wu K. Ung Y.C. Hornby J. et al. PET CT thresholds for radiotherapy target definition in non–small-cell lung cancer: How close are we to the pathologic findings?. Int J Radiat Oncol Biol Phys. 2010; 77: 699-706 Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar ). Other recent studies also showed the limitations of fixed thresholding and proposed more accurate and robust methods, from adaptive thresholding ( 4 Daisne J.-F. Sibomana M. Bol A. et al. Tri-dimensional automatic segmentation of PET volumes based on measured source-to-background ratios: Influence of reconstruction algorithms. Radiother Oncol. 2003; 69: 247-250 Abstract Full Text Full Text PDF PubMed Scopus (331) Google Scholar , 5 Nestle U. Kremp S. Schaefer-Schuler A. et al. Comparison of different methods for delineation of 18F-FDG PET-positive tissue for target volume definition in radiotherapy of patients with non-small cell lung cancer. J Nucl Med. 2005; 46: 1342-1348 PubMed Google Scholar ) to advanced algorithms ( 6 Geets X. Lee J.A. Bol A. et al. A gradient-based method for segmenting FDG-PET images: Methodology and validation. Eur J Nucl Med Mol Imaging. 2007; 34: 1427-1438 Crossref PubMed Scopus (330) Google Scholar , 7 Montgomery D.W.G. Amira A. Zaidi H. Fully automated segmentation of oncological PET volumes using a combined multiscale and statistical model. Med Phys. 2007; 34: 722-736 Crossref PubMed Scopus (93) Google Scholar , 8 Hatt M. Cheze le Rest C. Descourt P. et al. Accurate automatic delineation of heterogeneous functional volumes in positron emission tomography for oncology applications. Int J Radiat Oncol Biol Phys. 2010; 77: 301-308 Abstract Full Text Full Text PDF PubMed Scopus (148) Google Scholar ) capable in some cases of handling heterogeneous uptake frequently characterizing tumors treated with radiotherapy. Defining Radiotherapy Target Volumes Using 18F-Fluoro-Deoxy-Glucose Positron Emission Tomography/Computed Tomography: Still a Pandora's Box?International Journal of Radiation Oncology, Biology, PhysicsVol. 78Issue 5PreviewWe discuss the effect of 18F-fluoro-deoxy-glucose (FDG) positron emission tomography (PET)/computed tomography (CT) data on target volume definition for radiotherapy planning. We compared the effect of various thresholding methods on the PET-based target volume vs. the standard CT-based tumor volume. Full-Text PDF