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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).

KEY POINTS

  • 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 thelancet.com.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
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