The impact of F-18-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) lymph node staging on the radiation treatment volumes in patients with non-small cell lung cancer

Purpose: F-18-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PE T) combined with computer tomography (PET-CT) is superior to CT alone in me diastinal lymph node (LN) staging in non-small cell lung cancer (NSCLC). We studied the potential impact of this non-invasive LN staging procedure on the radiation treatment plan of patients with NSCLC. Patients and methods: The imaging and surgical pathology data from 105 pati ents included in two previously published prospective LN staging protocols form the basis for the present analysis. For 73 of these patients, with pos itive LN's on CT and/or on PET, a theoretical study was performed in which for each patient the gross tumour volume (GTV) was defined based on CT and on PET-CT data. For each GTV, the completeness of tumour coverage was asses sed, using the available surgical pathology data as gold standard. A more d etailed analysis was done for the first ten consecutive patients in whom th e PET-CT-GTV was smaller than the CT-GTV. Theoretical radiation treatment p lans were constructed based an both CT-GTV and PET-CT-GTV. Dose-volume hist ograms for the planning target volume (PTV), for the total lung volume and the lung volume receiving more than 20 Gy (V-lung(20)) were calculated. Results: Data from 988 assessed LN stations were available. In the subgroup of 73 patients with CT or PET positive LN's, tumour coverage improved from 75% when the CT-GTV was used to 89% with the PET-CT-GTV (P = 0.005). In 45 patients (62%) the information obtained from PET would have led to a chang e of the treatment volumes. For the ten patients in the dosimetry study, th e use of PET-CT to define the GTV, resulted in an average reduction of the PTV by 29 +/- 188 (+/- 1 SD) (P = 0.002) and of the V-lung(20) of 27 +/- 18 % (+/- 1 SD) (P = 0.001). Conclusion: In patients with NSCLC considered for curative radiation treatm ent, assessment of locoregional LN tumour extension by PET will improve tum our coverage, and in selected patients, will reduce the volume of normal ti ssues irradiated, and thus toxicity. This subgroup of patients could then b ecome candidates for treatment intensification. (C) 2000 Elsevier Science I reland Ltd. All rights reserved.