Contrast-Enhanced Ultrasound Evaluates Pathological Response Grades After Neoadjuvant Therapy in Colorectal Liver Metastases.

RATIONALE AND OBJECTIVES: Precise assessment of pathological response grades after neoadjuvant therapy in colorectal liver metastases (CRLM) is essential for facilitating individualized therapeutic decision-making. OBJECTIVES: To establish a one-step contrast-enhanced ultrasound (CEUS) classification system to evaluate five grades of pathological response after neoadjuvant therapy in CRLM. MATERIALS AND METHODS: This study was conducted with CRLM who underwent preoperative CEUS following neoadjuvant therapy from January 2023 to December 2024. Pathological response was graded according to tumor regression grade (TRG) scheme. Accordingly, CEUS five-grade patterns were established based on perfusion characteristics of wash-in at arterial-phase and washout at portal vein and late phase, including: ①Non-enhanced, ②Slow In/Slow Out, ③Slow In/Fast Out, ④Fast In/Slow Out, ⑤Fast In/Fast Out. Inter-reader agreement was assessed using Cohen's kappa. Diagnostic performance of CEUS and concurrent contrast-enhanced MRI (CEMRI) were evaluated using McNemar's test and DeLong test (TRG 1-3: favorable pathological response; TRG 4-5: poor pathological response). RESULTS: A total of 217 patients (mean age 58±10 years; 148 male) were enrolled into this study. CEUS five-grade patterns were strongly correlated with five TRGs (Spearman r=0.812, P<0.001). In TRG 1-2, 82.1% (46/56) of the patients showed CEUS pattern ①-②. There were 32.4% (23/71) of the patients showed pattern ③ in TRG 3. 100% (90/90) of the patients showed Pattern ④-⑤ in TRG 4-5. Inter-reader agreement was good to excellent in CEUS five-grade patterns (κ=0.768-0.896). In the head-to-head comparison (n=128), CEUS demonstrated significantly higher sensitivity (100% vs. 67.3%, P < 0.001) and accuracy (82.8% vs. 75.0%, P=0.009) but lower specificity (71.1% vs. 80.3%, P=0.012) than CEMRI in tumor response. CONCLUSION: CEUS five-grade patterns provided a non-invasive method for evaluating pathological response to neoadjuvant therapy in CRLM. These findings support further investigation of CEUS as a complementary modality to CEMRI, particularly for patients lacking baseline imaging or with contraindications to CEMRI.