Standardized uptake value on 18F-FDG-PET/CT is a predictor of EGFR T790M mutation status in patients with acquired resistance to EGFR-TKIs

• We evaluated the association between FDG-PET metrics and EGFR T790M status.
• T790M status was significantly associated with the levels of SUVmean and SUVmax in FDG-PET/CT.
• The survival in patients who acquired T790M after failure of EGFR-TKIs was significantly longer than those without T790M.

BackgroundThe development of epidermal growth factor receptor (EGFR) T790M point mutation in exon 20 (T790M) is the most common mechanism of resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs). The purpose of this study was to determine the association of 18F-2-fluoro-2-deoxyglucose-positron emission tomography/computed tomography (FDG–PET/CT) metrics with T790M status after acquiring resitance to EGFR-TKI resistance.MethodsWe retrospectively reviewed 34 advanced non-small cell lung cancer (NSCLC) patients harboring EGFR mutation who underwent rebiopsy and FDG–PET/CT before rebiopsy. These patients were evaluated for baseline characteristics, initial response to EGFR–TKIs, site of rebiopsy, overall survival, and FDG–PET/CT metrics, such as standardized uptake value (SUV), metabolic tumor volume, and total lesion glycolysis of the rebiopsy site.ResultsThe median age was 67 years (range, 37–86 years); 19 of the patients (56%) were men. Histologic examination revealed adenocarcinoma in all but one patient, with 20 patients (59%) having stage IIIB and IV disease. Upon initial mutational analyses, the types of EGFR mutation included 17 (50%) deletions in exon 19 and 17 (50%) L858R point mutations in exon 21. At the time of acquired resistance to EGFR-TKIs, T790M mutation was identified in 20 (59%) patients. T790M-positive patients had significantly lower levels of median SUVmean and median SUVmax of the rebiopsy site on FDG–PET/CT, compared with T790M-negative patients (SUVmean: 4.57 vs. 9.91, P = 0.0069; SUVmax: 7.26 vs. 16.06, P = 0.0054). The survival in patients who acquired T790M after failure of EGFR-TKIs was significantly longer than those without T790M (10.2 mos. vs. 18.6 mos., P < 0.05).ConclusionT790M status was associated with lower levels of SUVmean and SUVmax on FDG–PET/CT and significantly longer survival.