Relationship between 18F-FDG PET/CT radiometabolic markers and EGFR mutation, positive ALK Expression in patients with non-small cell lung cancer.

Introduction: The aim of this study was to evaluate the association between the presence of EGFR mutations, ALK rearrangement and the standardized uptake value (SUV) of 18F-fluoro-2-deoxy-glucose (18F-FDG) by PET/CT imaging in patients with NSCLC.

Materials and methods: We retrospectively reviewed NSCLC patients, who underwent EGFR mutation, ALK rearrangement testing and pre-treatment PET/ CT. The relationships of EGFR mutation, ALK rearrangement with patient characteristics and three parameters based on 18F-FDG PET/CT, including the maximal standard uptake value (SUVmax) of the primary tumour (tSUVmax), lymph node (nSUVmax) and distant metastasis (mSUVmax) were evaluated.

Result: EGFR mutations were found more frequently in females and nonsmokers. tSUVmax was the only PET parameter that was lower in EGFRpositive patients than in EGFR-negative patients (8.7 vs. 11), with a p value of 0.032. There were no differences between nSUVmax and mSUVmax results and EGFR mutation. tSUVmax, nSUVmax and mSUVmax were not significantly different between ALK positive and ALK negative groups in NSCLC. The presence of pleural fluid at the time of diagnosis was significantly associated with positive ALK expression.

Conclusions: We showed that low tSUVmax and primary tumour diameter were associated with mutant EGFR status and could be evaluated with other clinical factors to increase the discrimination in EGFR mutation status in some NSCLC patients without EGFR testing. There is a correlation between ALK positivity and the presence of pleural fluid. We also noted that the ALK positivity might be only in the adenocarcinoma group and at a younger age.