Dual-energy spectral CT characteristics in surgically resected lung adenocarcinoma: comparison between Kirsten rat sarcoma viral oncogene mutations and epidermal growth factor receptor mutations

Abstract

Background: Kirsten rat sarcoma viral oncogene homolog (KRAS) and epidermal growth factor receptor (EGFR) are the two most frequent and well-known oncogene of lung adenocarcinoma. The purpose of this study is to compare the characteristics measured with dual-energy spectral computed tomography (DESCT) in lung adenocarcinoma patients who have KRAS and EGFR gene mutations.

Methods: Patients with surgically resected lung adenocarcinoma (n = 72) were enrolled, including 12 patients with KRAS mutations and 60 patients with EGFR mutations. DESCT quantitative parameters, including the CT number at 70 keV, the slopes of the spectral attenuation curves (slope λ HU), normalized iodine concentration (NIC), normalized water concentration (NWC), and effective atomic number (effective Z), were analyzed. A multiple logistic regression model was applied to discriminate clinical and DESCT characteristics between the types of mutations.

Results: The KRAS mutation was more common in people who smoked than the EGFR mutation. Nodule type differed significantly between the KRAS and EGFR groups (P = 0.035), and all KRAS mutation adenocarcinomas were solid nodules. Most DESCT quantitative parameters differed significantly between solid nodules and subsolid nodules. CT number at 70 keV, slope λ HU, NIC, and effective Z differed significantly between the KRAS and EGFR groups (P = 0.006, 0.017, 0.013 and 0.010) with solid lung adenocarcinoma. Multivariate logistic analysis of DESCT and clinical features indicated that besides smoking history, the CT value at 70 keV (OR = 0.938, P = 0.009) was significant independent factor that could be used to differentiate KRAS and EGFR mutations in solid lung adenocarcinoma.

Conclusions: DESCT would be a potential tool to differentiate lung adenocarcinoma patients with a KRAS mutation from those with an EGFR mutation.

Keywords: Adenocarcinoma of lung; Dual-energy spectral computed tomography; EGFR mutation; KRAS mutation; Solid nodule; Subsolid nodule.

Fig. 1

Flowchart depicting the patient selection

Fig. 2

Male, 73 years old, lung adenocarcinoma with KRAS mutation. (a) A DESCT 70 keV image showed a solid nodule in the middle lobe of the right lung; the CT number at 70 keV was 11.49 Hu. (b) An iodine-based material-decomposition image reveals that the iodine concentration (IC) of the nodule is 9.06 μg/cm3 (L1). The IC of the aorta is 77.24 μg/cm3. The normalized IC (NIC) of this lung adenocarcinoma is 0.12 (9.06/77.24). (c) The effective Z material-decomposition image shows that the effective Z of the nodule is 8.15. (d) The graph shows the spectral HU curve of the nodule. Slope λ HU is 1.01. (e) The molecular pathological results showed KRAS mutations

Fig. 3

Female, 39 years old, lung adenocarcinoma with EGFR mutation. (a) A DESCT 70 keV image showed a solid nodule in the inferior lobe of the left lung. The CT number at 70 keV was 49.66 HU. (b) An iodine-based material-decomposition image shows that the iodine concentration (IC) of the nodule is 12.18 μg/cm3; the IC of the aorta is 76.23 μg/cm3; the normalized IC (NIC) of this lung adenocarcinoma is 0.16 (12.18/76.23). (c) The effective Z material-decomposition image shows that the effective Z of the nodule is 8.35. (d) The graph shows the spectral HU curve of the nodule; slope λ HU is 0.82. (e) The molecular pathological results showed EGFR mutations

Fig. 4

Graph shows the receiver operating characteristic (ROC) curve for discrimination of patients with KRAS mutations from those with EGFR mutations at DESCT (CT number at 70 keV) including and not including smoking in solid lung adenocarcinoma. The area under curve (AUC) of CT number at 70 keV is 0.771 with the cutoff point of 38.47 HU. The AUC of combination of CT number at 70 keV and smoking is 0.841 with the cutoff point of 2.72