Purpose: To explore the value of parameters of the on hepatobiliary phase (HBP) of pre-treatment gadoxetic acid-enhanced magnetic resonance imaging (MRI) for predicting pathological response to systemic therapy in colorectal liver metastases (CRLMs), compared with response evaluation criteria in solid tumors, version 1.1 (RECIST 1.1).
Methods: A total of 96 patients with CRLMs who underwent gadoxetic acid-enhanced MRI prior to treatment and then liver resection from January 2017 to December 2021 were enrolled. The pathological response was assessed by the percentage of residual tumors (RTs), and CRLMs were classified into two groups according to the pathological response grade (PRG): (1) strong response (including PRG2 and PRG3, RTs ≤ 10%), and weak response (PRG1, RTs > 10%). Two radiologists evaluated the enhancement pattern and degree of CRLMs on the HBP. The diameter, mean and standard deviation (SD) value of signal intensity (SI) of CRLMs on pre-contrast and HBP images were recorded. Relative tumor enhancement (RTE) and the SD ratio (SDR) were calculated. These parameters were analyzed in terms of pathological response on a lesion-by-lesion basis.
Results: Totally, 263 CRLMs were classified into: the strong response group (PRG2, n = 57; PRG3, n = 7) and the weak response group (PRG1, n = 199). RTE and SDR values were significantly higher in the strong response group than in the weak response group (P < 0.001). RTE values (P < 0.001) and SDR values (P = 0.031) were independent factors for predicting strong response. The area under curve (AUC) of RTE and SDR values were 0.725 and 0.652, respectively. The combination of these parameters was 0.750, which performed better than RECIST 1.1 (0.750 vs 0.531; P < 0.001).
Conclusions: RTE and SDR values on HBP are potential features in predicting pathological response to systemic therapy in CRLMs.
Keywords: Colorectal liver metastases; Hepatobiliary phase; Magnetic resonance imaging; Pathological response.
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