medwireNews: Target volume reduction based on 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) may be superior to conventional target volume planning for local control in patients with locally advanced non-small-cell lung cancer (NSCLC), research shows.
Patients who received 18F-FDG PET-based planning also experienced similar toxicities to those who received conventional treatment, leading the study investigators to say: “Imaging-based target volume reduction in this setting is, therefore, feasible, and could potentially be considered standard of care.”
The multicenter PET-Plan study included 205 previously untreated patients with inoperable stage II–III NSCLC suitable for chemoradiotherapy. They were randomly assigned to receive a target irradiation volume determined by 18F-FDG PET with no elective nodal irradiation or to the conventional method informed by 18F-FDG PET and computed tomography (CT) plus elective nodal irradiation. In both groups, dose-escalated radiotherapy (60–74 Gy, 2 Gy per fraction) was planned to the respective target volumes and given in conjunction with platinum-based chemotherapy.
As reported in The Lancet Oncology, individuals in the 18F-FDG PET-based target group received significantly higher mean escalated total radiotherapy reference dose than those in the conventional target group, at 67.3 vs 65.3 Gy, and were significantly more likely to achieve a dose of 68 Gy or more (47 vs 33%).
At 1 year, the locoregional progression rates were 14% among the 88 patients treated according to the protocol in the 18F-FDG PET-based target group and 29% among the 84 per-protocol treated patients in the conventional group.
And at a median 29 months of follow-up, the primary study endpoint of noninferiority was met, with the hazard ratio for locoregional progression of 0.57 with 18F-FDG PET versus conventional target planning falling below the prespecified limit of 1.25.
Median overall and progression-free survival were similar between the two groups, at 2.41 and 0.92 years, respectively, with 18F-FDG PET-based targeting, and 3.08 and 0.85 years, respectively with conventional targeting.
Ursula Nestle (Kliniken Maria Hilf, Mönchengladbach, Germany) and co-investigators found that treatment-related toxicities “were generally mild to moderate.” The most common acute toxicity of grade 3 or higher was esophagitis or dysphagia, occurring in 16% of patients in both the 18F-FDG PET-based (n=105 for safety analysis) and conventional (n=99) target groups. The most common grade 3 or above late toxicities were lung-related and occurred in 11% and 12%, respectively.
There were 13 deaths potentially related to the study treatment in the 18F-FDG PET group and seven in the conventional group, of which 11 and six, respectively, were of pulmonary origin.
Nestle and co-authors believe their study is the first of its kind to provide “prospective, quality-controlled evidence showing that the restriction of target volumes based on molecular imaging information in the context of a dose-escalated chemoradiotherapy is non-inferior to conventional planning and, furthermore, might lead to improved local outcomes without increased toxicity.”
“We, therefore, believe that the target volume delineation established in the PET-Plan trial could be considered standard of care and could be used in future trials aiming to improve systemic treatment along with optimum radiotherapy.”
In an accompanying comment, Corinne Faivre-Finn, from The Christie NHS Foundation Trust in Manchester, UK, agrees with this conclusion and adds that “PET-Plan is an important practice- confirming study in the field of thoracic radiotherapy.”
She says: “[T]he PET-Plan study has confirmed that less can be more in the field of thoracic radiotherapy and that involved field radiotherapy guided by PET/CT could be considered the standard of care. This message is important in the era of immunoradiotherapy combinations.”
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Lancet Oncol 2020; doi: 10.1016/S1470-2045(20)30013-9
Lancet Oncol 2020; doi: 10.1016/S1470-2045(20)30108-X