Less is more in radiotherapy target volume planning: lessons from the PET-plan trial
Mené sur 311 patients atteints d'un cancer du poumon non à petites cellules de stade localement avancé (durée médiane de suivi : 29 mois), cet essai international (Allemagne, Autriche et Suisse) évalue la non infériorité, par rapport à une planification volumétrique conventionnelle et du point de vue du délai avant la progression locorégionale de la tumeur, d'une planification visant à réduire, dans le cadre d'une chimioradiothérapie radicale, le volume tissulaire ciblé au moyen d'une tomographie par émission de positrons à base de fluorodésoxyglucose (18F)
In The Lancet Oncology, Ursula Nestle and colleagues report a randomised, controlled trial of image-based radiotherapy target volumes for patients with stage II–III non-small-cell lung cancer. Patients suitable for concurrent chemoradiotherapy were randomly assigned to a target volume informed by 18F-fluorodeoxyglucose ( 18F-FDG) PET and CT plus elective nodal irradiation or by 18F-FDG-PET alone without elective nodal irradiation. In both groups, the dose of radiation was escalated (60–74 Gy, 2 Gy per fraction) and prescribed for each individual patient on the basis of predefined normal tissue constraints (the concept of isotoxic radiotherapy). The study used a non-inferiority design with a primary endpoint of time to locoregional progression from randomisation. It can be concluded from this study that target volume reduction based on 18F-FDG PET alone was not inferior to traditional large volume radiotherapy with elective nodal irradiation with regard to locoregional control, with a suggestion of improvement in locoregional control; allowed further escalation of the radiation dose; and was not associated with a substantial reduction or increase in toxicity. However, given the design and results of the study, it is not possible to draw conclusions on the superiority of the target volume reduction strategy with regard to locoregional control or survival; the impact of the isotoxic dose escalation; or the association between study endpoints and dose-volume histograms (particularly heart dose). In view of the result of this study, target volume reduction based on 18F-FDG PET alone could be considered standard of care. International guidelines already recommend the omission of elective nodal irradiation guided by 18F-FDG PET/CT in locally advanced non-small-cell lung cancer, making this study practice confirming.