Abstract
18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) has the potential to improve the staging and radiation treatment (RT) planning of various tumor sites. However, from a clinical standpoint, questions remain with regard to what extent PET/CT changes the target volume and whether PET/CT reduces interobserver variability in target volume delineation. The present study analyzed the use of FDG-PET/CT images for staging and evaluated the impact of FDG-PET/CT on the radiotherapy volume delineation compared with CT in patients with non-small cell lung cancer (NSCLC) who were candidates for radiotherapy. Intraobserver variation in delineating tumor volumes was also observed. In total, 23 patients with stage I-III NSCLC were enrolled and treated with fractionated RT-based therapy with or without chemotherapy. FDG-PET/CT scans were acquired within two weeks prior to RT. PET and CT data sets were sent to the treatment planning system, Pinnacle, through compact discs. The CT and PET images were subsequently fused by means of a dedicated RT planning system. Gross tumor volume (GTV) was contoured by four radiation oncologists on CT (GTV-CT) and PET/CT images (GTV-PET/CT). The resulting volumes were analyzed and compared. For the first phase, two radiation oncologists outlined the contours together, achieving a final consensus. Based on PET/CT, changes in tumor-node-metastasis categories occurred in 8/23 cases (35%). Radiation targeting with fused FDG-PET and CT images resulted in alterations in radiation therapy planning in 12/20 patients (60%) in comparison with CT targeting. The most prominent changes in GTV were observed in cases with atelectasis. For the second phase, the variation in delineating tumor volumes was assessed by four observers. The mean ratio of largest to smallest CT-based GTV was 2.31 (range, 1.01–5.96). The addition of the PET results reduced the mean ratio to 1.46 (range, 1.02–2.27). PET/CT fusion images may have a potential impact on tumor staging and treatment planning. Implementing matched PET/CT results reduced observer variation in delineating tumor volumes significantly with respect to CT only.
Highlights
In locally advanced non‐small cell lung cancer (NSCLC), definitive radiation treatment (RT) provides improved disease control and survival rates through high‐dose radiation and concurrent administration of systemic drugs
Three patients were diagnosed with metastatic disease based on FDG‐positron emission tomography (PET)/computed tomography (CT) and received palliative chemotherapy
The PET image was always considered as additional information to the CT image for tumor staging or target contouring for treatment planning
Summary
In locally advanced non‐small cell lung cancer (NSCLC), definitive radiation treatment (RT) provides improved disease control and survival rates through high‐dose radiation and concurrent administration of systemic drugs. There is considerable interest in investigating functional imaging, including positron emission tomography (PET) with 18F‐fluorodeoxyglucose (FDG), that provides improved tumor staging, delineation of the target volume, identification of the treatment response and detection of recurrence for a wide range of solid cancer types [1,2,3]. A range of image registration strategies allows FDG‐PET images to be directly incorporated into computed tomography (CT) images. This allows the complementary strengths of functional (PET) and structural (CT) imaging to be co‐registered in a single image set
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