Prognostic value of multi b -value DWI in patients with locally advanced rectal cancer

Objectives To evaluate the potential of multi b -value DWI in predicting the prognosis of patients with locally advanced rectal cancer (LARC). Methods From 2015 to 2019, a total of 161 patients with LARC were enrolled and randomly sampled into a training set ( n = 113) and validation set ( n = 48). Multi b -value DWI ( b = 0~1500 s/mm 2 ) scans were postprocessed to generate functional parameters, including apparent diffusion coefficient (ADC), Dt, Dp, f , distributed diffusion coefficient (DDC), and α. Histogram features of each functional parameter were submitted into Least absolute shrinkage and selection operator (LASSO) and stepwise multivariate COX analysis to generate DWI_score based on the training set. The prognostic model was constructed with functional parameter, DWI_score, and clinicopathologic factors by using univariate and multivariate COX analysis on the training set and verified on the validation set. Results Multivariate COX analysis revealed that DWI_score was an independent indicator for 5-year progression-free survival (PFS, HR = 5.573, p < 0.001), but not for overall survival (OS, HR = 2.177, p = 0.051). No mean value of functional parameters was correlated with PFS or OS. Prognostic model for 5-year PFS based on DWI_score, TNM-stage, mesorectal fascia (MRF), and extramural venous invasion (EMVI) showed good performance both in the training set (AUC = 0.819) and validation set (AUC = 0.815). Conclusions The DWI_score based on histogram features of multi b -value DWI functional parameters was an independent factor for PFS of LARC and the prognostic model with a combination of DWI_score and clinicopathologic factors could indicate the progression risk before treatment. Key Points • Mean value of functional parameters obtained from multi b-value DWI might not be useful to assess the prognosis of LARC. • The DWI_score based on histogram features of multi b-value DWI functional parameters was an independent prognosis factor for PFS of LARC. • Prognostic model based on DWI_score and clinicopathologic factors could indicate the progression risk of LARC before treatment.