Imaging-Based Radiotherapy Target Volume Reduction in Locally Advanced NSCLC

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In a European trial (PET-Plan) reported in The Lancet Oncology, Nestle et al found that the use of reduced radiotherapy target volumes determined by 18F-fluorodeoxyglucose positron-emission tomography (FDG-PET) alone may achieve improved local control vs conventional target planning with FDG-PET/computed tomography (CT) plus elective nodal irradiation in patients receiving chemoradiotherapy for locally advanced non–small cell lung cancer (NSCLC).  

Study Details

In the open-label trial—performed at sites in Austria, Germany, and Switzerland—205 patients undergoing FDG-PET and CT for treatment planning were randomly assigned to target volume delineation with FDG-PET and CT plus elective nodal irradiation (conventional target group, n = 99) or target volumes planned by PET alone (FDG-PET–based target group, n = 106). A total of 172 patients were treated per protocol, consisting of 84 in the conventional target group and 88 in the FDG-PET–based target group. For patients in both groups, dose-escalated radiotherapy (60–74 Gy, 2 Gy per fraction) was planned to the respective target volumes and given concurrently with platinum-based chemotherapy.

The primary endpoint was time to locoregional progression, with the aim of testing noninferiority of FDG-PET–based planning with a prespecified hazard ratio (HR) margin of 1.25. The primary analysis was performed in the per-protocol population.

Locoregional Progression

Median follow-up was 29 months. At 1 year, the risk of locoregional progression in the per-protocol population was 14% in the FDG-PET–based target group vs 29% in the conventional target group (HR = 0.57, 95% confidence interval [CI] = 0.30–1.06), satisfying the criterion for noninferiority. In intention-to-treat analysis, outcome in the FDG-PET–based target group was also numerically better and statistically noninferior to that in the conventional target group: at 1 year, the risk of locoregional progression was 17% vs 30% (HR = 0.64, 95% CI = 0.37–1.10).


  • At 1 year, risk of locoregional progression in the per-protocol population was 14% in the FDG-PET-based target group vs 29% in the conventional target group.
  • In the intention-to-treat population, 1-year risk was 17% vs 30%.

Adverse Events

The most common acute grade ≥ 3 toxicities among all patients were esophagitis or dysphagia, occurring in 16% of the conventional target group vs 16% of the 18F-FDG PET-based target group, and hematologic toxicity (20% vs 30%). The most common late-grade 3 or 4 toxicities were lung-related (12% vs 10%). The numbers of treatment-related serious adverse events were 14 vs 15, consisting primarily of infections (9 vs 9). Potentially treatment-related death occurred in 7 patients in the conventional target group vs 13 patients in the FDG-PET–based target group; 17 were due to pulmonary causes (6 vs 11, including pneumonia in 4 vs 5).

The investigators concluded, “18F-FDG PET-based planning could potentially improve local control and does not seem to increase toxicity in patients with chemoradiotherapy-treated locally advanced NSCLC. Imaging-based target volume reduction in this setting is, therefore, feasible, and could potentially be considered standard of care. The procedures established might also support imaging-based target volume reduction concepts for other tumors.”

Ursula Nestle, MD, of the Department of Radiation Oncology, University of Freiburg, is the corresponding author for The Lancet Oncology article.

Disclosure: The study was funded by German Cancer Aid (Deutsche Krebshilfe). For full disclosures of the study authors, visit

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