Iodine-related attenuation in contrast-enhanced dual-energy computed tomography in small-sized solid-type lung cancers is associated with the postoperative prognosis

Abstract

Background: To investigate the correlation between iodine-related attenuation in contrast-enhanced dual-energy computed tomography (DE-CT) and the postoperative prognosis of surgically resected solid-type small-sized lung cancers.

Methods: We retrospectively reviewed the DE-CT findings and postoperative course of solid-type lung cancers ≤3 cm in diameter. After injection of iodinated contrast media, arterial phases were scanned using 140-kVp and 80-kVp tube voltages. Three-dimensional iodine-related attenuation (3D-IRA) of primary tumors at the arterial phase was computed using the "lung nodule" application software. The corrected 3D-IRA normalized to the patient's body weight and contrast medium concentration was then calculated.

Results: A total of 120 resected solid-type lung cancers ≤3 cm in diameter were selected for analysis (82 males and 38 females; mean age, 67 years). During the observation period (median, 47 months), 32 patients showed postoperative recurrence. Recurrent tumors had significantly lower 3D-IRA and corrected 3D-IRA at early phase compared to non-recurrent tumors (p = 0.046 and p = 0.027, respectively). The area under the receiver operating characteristic curve for postoperative recurrence was 0.624 for the corrected 3D-IRA at early phase (p = 0.025), and the cutoff value was 5.88. Kaplan-Meier curves for disease-free survival indicated that patients showing tumors with 3D-IRA > 5.88 had a significantly better prognosis than those with tumors showing 3D-IRA < 5.88 (p = 0.017).

Conclusions: The 3D-IRA of small-sized solid-type lung cancers on contrast-enhanced DE-CT was significantly associated with postoperative prognosis, and low 3D-IRA tumors showed a higher TNM stage and a significantly poorer prognosis.

Keywords: Contrast enhancement; Dual-energy CT; Functional imaging; Iodine-related attenuation; Lung cancer.

Fig. 1

Study cohort flowchart. After applying the exclusion criteria, 120 small-sized (pathological tumor size ≤3 cm in diameter) solid-type lung cancers were included in the present analysis

Fig. 2

A 68-year-old male patient. An adenocarcinoma (pT2aN0) is observed in the left upper lobe. a Lung window setting. b Mediastinal window setting at the early phase of contrast-enhanced CT. c Iodine-enhanced image in contrast-enhanced CT. The 3D-IRA is 30 HU, and the corrected 3D-IRA is 4.59. The patient developed recurrence of adrenal metastases at 15 months after a left upper lobectomy

Fig. 3

A 75-year-old female patient. A squamous cell carcinoma (pT1bN0) is observed in the left lower lobe. a Lung window setting. b Mediastinal window setting at the early phase of contrast-enhanced CT. c Iodine-enhanced image in contrast-enhanced CT. The 3D-IRA is 48 HU, and the corrected 3D-IRA is 6.45. The patient was recurrence-free for 51 months after a left lower lobectomy

Fig. 4

The graph shows Kaplan–Meier curves for disease-free survival according to the corrected 3D-IRA at the early phase of contrast-enhanced CT. a Patients with tumors showing 3D-IRA > 5.88 had a significantly better prognosis than those with tumors showing 3D-IRA < 5.88 (p = 0.017). b Patients with adenocarcinomas, c patients with squamous cell carcinomas, d patients with other subtype tumors showing 3D-IRA > 5.88 had a better prognosis than those with tumors showing 3D-IRA < 5.88 although there was no significant difference (p = 0.224, p = 0.126, and p = 0.109, respectively)