OBJECTIVES: To compare diagnostic accuracy of contrast-enhanced CT, dual-layer detector spectral CT (DL-CT), and whole-body MRI (WB-MRI) for diagnosing metastatic breast cancer.

METHODS: One hundred eighty-two biopsy-verified breast cancer patients suspected of metastatic disease prospectively underwent contrast-enhanced DL-CT and WB-MRI. Two radiologists read the CT examinations with and without spectral data in consensus with 3-month washout between readings. Two other radiologists read the WB-MRI examinations in consensus. Lymph nodes, visceral lesions, and bone lesions were assessed. Readers were blinded to other test results. Reference standard was histopathology, previous or follow-up imaging, and clinical follow-up.

RESULTS: Per-lesion AUC was 0.80, 0.84, and 0.82 (CT, DL-CT, and WB-MRI, respectively). DL-CT showed significantly higher AUC than CT (p = 0.001) and WB-MRI (p = 0.02). Sensitivity and specificity of CT, DL-CT, and WB-MRI were 0.66 and 0.94, 0.75 and 0.95, and 0.65 and 0.98, respectively. DL-CT significantly improved sensitivity compared to CT (p < 0.0001) and WB-MRI (p = 0.002). Per-patient AUC was 0.85, 0.90, and 0.92 (CT, DL-CT, and WB-MRI, respectively). DL-CT and WB-MRI had significantly higher AUC than CT (p = 0.04 and p = 0.03). DL-CT significantly increased sensitivity compared to CT (0.89 vs. 0.79, p = 0.04). WB-MRI had significantly higher specificity than CT (0.84 vs. 0.96, p = 0.001) and DL-CT (0.87 vs. 0.96, p = 0.02).

CONCLUSIONS: DL-CT showed significantly higher per-lesion diagnostic performance and sensitivity than CT and WB-MRI. On a per-patient basis, DL-CT and WB-MRI had equal diagnostic performance superior to CT.

KEY POINTS: • Spectral CT has higher diagnostic performance for diagnosing breast cancer metastases compared to conventional CT and whole-body MRI on a per-lesion basis. • Spectral CT and whole-body MRI are superior to conventional CT for diagnosing patients with metastatic breast cancer. • Whole-body MRI is superior to conventional CT and spectral CT for diagnosing bone metastases.