Objectives: For the ultimately efficient screening of anaplastic lymphoma kinase gene (ALK)-positive cases, combination of radiometabolic characteristics with clinicopathologic features may be more useful. Therefore, we determined radiologic characteristics and metabolic characteristics in patients with adenocarcinoma harboring ALK mutations.
Patients and methods: We retrospectively reviewed clinicopathologic CT and PET/CT data from patients with advanced lung adenocarcinoma screened for identifying ALK rearrangement. Lesion size, solidity, location, margins, CT attenuation, and SUVmax were assessed. Pathologic features such as differentiation, the presence of signet ring cell, EGFR/KRAS mutation status, and TTF-1 expression were also reviewed.
Results: Of the screened 221 patients, 41 patients (19%) demonstrated ALK rearrangements, and these individuals were younger than the ALK-negative patients (P < 0.001) and showed significant association with no exposure to tobacco (P = 0.028). ALK-positive lung adenocarcinomas were significantly less differentiated than those without rearrangements (P = 0.005). ALK-positive tumors showed significantly higher SUVmax than ALK-negative tumors (P = 0.016). Multivariate logistic regression modeling for predicting the ALK-positive lung adenocarcinoma disclosed that lower CT attenuation and higher SUVmax were significant independent factors of ALK rearrangements (odds ratio, 0.87 and 1.06; P = 0.03 and 0.01, respectively). Receiver operating characteristic analysis showed that the area under the receiver operating characteristic curve for SUVmax/CT attenuation ratio was 0.788, and the optimal cutoff value of SUVmax/CT attenuation ratio for identifying ALK-positive lung adenocarcinoma was greater than or equal to 0.208 (sensitivity, 74.2%; specificity, 81.0%).
Conclusions: This study shows that ALK-rearranged lung adenocarcinoma represents younger age, no history of smoking, the absence of spiculation on CT, and higher SUVmax/CT attenuation greater than or equal to 0.208 compared with those without ALK mutation.