Purpose: The aim of this study was to investigate the impact of a hybrid fluorodeoxyglucose positron-emission tomography/computed tomography (FDG-PET/CT) scanner in radiotherapy planning for esophageal and non-small-cell lung cancer (NSCLC).
Methods and materials: A total of 30 patients (16 with esophageal cancer, 14 with NSCLC) underwent an FDG-PET/CT for radiotherapy planning purposes. Noncontrast total-body spiral CT scans were obtained first, followed immediately by FDG-PET imaging which was automatically co-registered to the CT scan. A physician not involved in the patients' original treatment planning designed a gross tumor volume (GTV) based first on the CT dataset alone, while blinded to the FDG-PET dataset. Afterward, the physician designed a GTV based on the fused PET/CT dataset. To standardize PET GTV margin definition, background liver PET activity was standardized in all images. The CT-based and PET/CT-based GTVs were then quantitatively compared by way of an index of conformality, which is the ratio of the intersection of the two GTVs to their union.
Results: The mean index of conformality was 0.44 (range, 0.00-0.70) for patients with NSCLC and 0.46 (range, 0.13-0.80) for patients with esophageal cancer. In 10 of the 16 (62.5%) esophageal cancer patients, and in 12 of the 14 (85.7%) NSCLC patients, the addition of the FDG-PET data led to the definition of a smaller GTV.
Conclusion: The incorporation of a hybrid FDG-PET/CT scanner had an impact on the radiotherapy planning of esophageal cancer and NSCLC. In future studies, we recommend adoption of a conformality index for a more comprehensive comparison of newer treatment planning imaging modalities to conventional options.