PET-Planned Chemoradiotherapy ‘Noninferior’ For Locally Advanced NSCLC

Author: By Lynda Williams, Senior medwireNews Reporter 

medwireNews: Research suggests that it may be feasible to reduce the tumour target volume for inoperable locally advanced non-small-cell lung cancer (NSCLC) patients undergoing chemoradiotherapy using 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) treatment planning. 

The PET-Plan investigators report in The Lancet Oncology that 18F-FDG-PET target planning “could potentially improve local control and does not seem to increase toxicity” in this setting and therefore “could potentially be considered standard of care.” 

After a median 29 months of follow-up, the 1- and 3-year rates of locoregional progression were 14% and 23%, respectively, for the 88 patients who underwent 60–74 Gy of dose-escalated radiotherapy to a target volume based on 18F-FDG-PET. 

This compared with 1- and 3-year rates of 29% and 42%, respectively, for the 84 patients who underwent the same chemoradiotherapy dose based on 18F-FDG-PET and computed tomography information plus elective nodal irradiation. 

In the prespecified per-protocol analysis at 1 year, the hazard ratio (HR) for locoregional progression was 0.57 in favour of the PET-plan protocol, meeting the criteria for noninferiority compared with conventional treatment. 

The intention-to-treat locoregional progression analysis, per-protocol out-of-field progression analysis and per-protocol overall survival analysis did not show a significant difference between the two treatment arms, and the groups had comparable rates for metastasis at first site of progression. 

The researchers note that the mean escalated total radiotherapy dose was significantly higher in the 18F-FDG-PET-based target group compared with controls (67.3 vs 65.3 Gy) and patients given PET-based treatment were significantly more likely to achieve a dose of 68 Gy or more (47 vs 33%). 

Treatment-related toxicity was “generally mild to moderate”, say Ursula Nestle, from Kliniken Maria Hilf in Mönchengladbach, Germany, and co-authors. 

Grade 3 or more severe oesophagitis or dysphagia occurred in 16% of both treatment groups, while 20% of the PET-planned arm and 30% of the conventional arm experienced haematological events at this severity. Late grade 3–4 toxicities mostly occurred in the lung, affecting 12% and 10%, respectively. 

The researchers note the PET-Plan findings “support the conclusions of earlier trials that elective irradiation of mediastinal lymph nodes is not beneficial” and “support current guidelines and practice” for locally advanced NSCLC. 

And they add that “as the irradiation of unaffected draining lymph nodes might decrease the radiotherapy-related immune response, this trial might encourage other clinical trials on imaging-based target volume reduction for other solid tumours, especially in the context of radioimmunotherapy.” 

Reference  

Nestle U, Schimek-Jasch T, Kremp S, et al. Imaging-based target volume reduction in chemoradiotherapy for locally advanced non-small-cell lung cancer (PET-Plan): a multicentre, open-label, randomised, controlled trial. Lancet Oncol; Advance online publication 12 March 2020. https://doi.org/10.1016/S1470-2045(20)30013-9