Quantitative parameters of magnetic resonance imaging cannot predict human epidermal growth factor receptor 2 (HER2) status in rectal cancer

Purpose: To retrospectively investigate whether magnetic resonance imaging (MRI) quantitative parameters can differentiate human epidermal growth factor receptor 2 (HER2) status in rectal cancer. Materials and methods: This study included 89 patients with surgically confirmed rectal cancer who underwent preoperative MRI from June 2014 to May 2019. Patients were divided into three groups: HER2 negative (HER2-Neg); HER2-low expression (HER2-L); and HER2 positive (HER2-Pos). Quantitative perfusion parameters derived from dynamic contrast-enhanced MRI (DCE-MRI) Tofts model (pharmacokinetic blood dual compartment model) were listed as follows: volume transfer constant (K-trans), rate constant (K-ep), and extracellular volume ratio (V-e). The mean, minimum, and maximum apparent diffusion coefficient (ADC) values at standard (800 s/mm(2)) b-values were obtained with diffusion-weighted imaging (DWI). Clinicopathologic characteristics and quantitative parameters were compared by Fisher's exact test and one-way analysis of variance (ANOVA), respectively. Results: The 89 patients included 52 (58.4%) with HER2-Neg, 31 (34.8%) with HER2-L, and 6 (6.8%) with HER2-Pos states. Fisher's exact test showed that clinicopathologic characteristics among the three groups were not significantly different (p = 0.281 to 1.000). Likewise, there were no associations between HER2 status and any quantitative parameters, including K-trans (p = 0.296), K-ep (p = 0.290), V-e (p = 0.184), ADC(mean) (p = 0.181), ADC(min) (p = 0.143), or ADC(max) (p = 0.058). Conclusion: Quantitative perfusion parameters (K-trans, K-ep, V-e) and ADC values were not able to discriminate HER2 status in patients with rectal cancer or evaluate treatment response in real time.