In ALK-positive advanced NSCLC, crizotinib has a high response rate and effectively increases quality of life and survival. CT measurement of the tumor may insufficiently reflect the actual tumor load changes during targeted therapy with crizotinib. We explored whether 18F-FDG PET measured metabolic changes are different from CT based changes and studied the impact of these changes on disease progression.
Patients with advanced EML4/ALK positive NSCLC treated with crizotinib were studied with 18F-FDG PET/CT at baseline and after six weeks of treatment. During and after treatment patients underwent PET/CT until progression of disease was determined. If they were eligible for additional treatment (local treatment or systemic treatment with a second generation ALK inhibitor), PET/CT was repeated to assess tumor response again until disease progression was determined.
18F-FDG PET/CT was performed prior to and after 6 weeks of crizotinib treatment. Tumor response on CT was classified with RECIST 1.1, while 18F-FDG PET response was assessed according to the 1999 EORTC recommendations and PERCIST criteria. Agreement was assessed using McNemars test. During follow-up, patients received additional PET/CT during crizotinib treatment and second generation ALK inhibition. We assessed whether PET was able to detect progression earlier then CT.