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• 18F-afatinib PET/CT is a safe tool to quantify 18F-afatinib uptake in NSCLC tumors. • Tumor uptake of 18F-afatinib is higher in EGFR mutated NSCLC versus wild type EGFR. • There is no difference in tracer uptake between EGFR common and uncommon mutations. • A TBR_WB 60−90 value of ≥6 is predictive of response to treatment using afatinib. Non-small cell lung cancer (NSCLC) tumors harboring common (exon19del, L858R) and uncommon (e.g. G719X, L861Q) activating epidermal growth factor receptor (EGFR) mutations are best treated with EGFR tyrosine kinase inhibitors (TKI) such as the first-generation EGFR TKI erlotinib, second-generation afatinib or third-generation osimertinib. However, identifying these patients through biopsy is not always possible. Therefore, our aim was to evaluate whether 18F-afatinib PET/CT could identify patients with common and uncommon EGFR mutations. Furthermore, we evaluated the relation between tumor 18F-afatinib uptake and response to afatinib therapy. 18F-afatinib PET/CT was performed in 12 patients: 6 EGFR wild type (WT), 3 EGFR common and 3 EGFR uncommon mutations. Tumor uptake of 18F-afatinib was quantified using TBR_WB 60−90 (tumor-to-whole blood activity ratio 60−90 min post-injection) for each tumor. Response was quantified per lesion using percentage of change (PC): [(response measurement (RM)–baseline measurement (BM))/BM]×100. Statistical analyses were performed using t-tests, correlation plots and sensitivity/specificity analysis. Twenty-one tumors were identified. Injected dose was 348 ± 31 MBq. Group differences were significant between WT versus EGFR (common and uncommon) activating mutations (p = 0.03). There was no significant difference between EGFR common versus uncommon mutations (p = 0.94). A TBR_WB 60−90 cut-off value of 6 showed the best relationship with response with a sensitivity of 70 %, a specificity of 100 % and a positive predictive value of 100 %. 18F-afatinib uptake was higher in tumors with EGFR mutations (common and uncommon) compared to WT. Furthermore, a TBR_WB 60−90 cut-off of 6 was found to best predict response to therapy. 18F-afatinib PET/CT could provide a means to identify EGFR mutation positive patients who benefit from afatinib therapy. [ABSTRACT FROM AUTHOR]