• Stephanie A Terezakis, Margie A Hunt, Alexander Kowalski, Patrick McCann, C Ross Schmidtlein, Anne Reiner, Mithat Gönen, Assen S Kirov, Anne Marie Gonzales, Heiko Schöder, and Joachim Yahalom.
• Department of Radiation Oncology Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
• Int. J. Radiat. Oncol. Biol. Phys. 2011 Nov 1; 81 (3): 615-22.

PurposePositron emission-tomography (PET) using 2-[(18)F]fluoro-2-deoxyglucose (FDG-PET) increases sensitivity and specificity of disease detection in lymphoma and thus is standard in lymphoma management. This study examines the effects of coregistering FDG-PET and computed tomography (CT) (PET/CT) scans on treatment planning for lymphoma patients.Methods And MaterialsTwenty-nine patients (30 positive PET scans) underwent PET/CT treatment planning from July 2004 to February 2007 and were retrospectively studied. For each patient, gross tumor volume was blindly contoured on the CT-only and PET/CT studies by a radiation oncologist. Treatment plans were generated for both the CT-only and PET/CT planning target volumes (PTVs) for all patients. Normal tissue doses and PTV coverage were evaluated using dose--volume histograms for all sites.ResultsThirty-two treatment sites were evaluated. Twenty-one patients had non-Hodgkin lymphoma, 5 patients had Hodgkin lymphoma, and 3 patients had plasma cell neoplasms. Previously undetected FDG-avid sites were identified in 3 patients during PET/CT simulation, resulting in one additional treatment field. Due to unexpected PET/CT simulation findings, 2 patients did not proceed with radiation treatment. The addition of PET changed the volume of 23 sites (72%). The PTV was increased in 15 sites (47%) by a median of 11% (range, 6-40%) and reduced in 8 sites (25%) by a median of 20% (range, 6%-75%). In six (19%) replanned sites, the CT-based treatment plan would not have adequately covered the PTV defined by PET/CT.ConclusionsIncorporation of FDG-PET into CT-based treatment planning for lymphoma patients resulted in considerable changes in management, volume definition, and normal tissue dosimetry for a significant number of patients.Copyright © 2011 Elsevier Inc. All rights reserved.

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