Background:The red blood cell distribution width (RDW) level is a potential prognostic factor for solid tumours.We aimed to investigate the predictive value of pre-neoadjuvant chemotherapy (pre-NAC) RDW, preoperative RDW and the change in RDW on the pathological response and prognosis of patients with colorectal liver metastasis (CRLM), which was helpful for treatment decision-making, surveillance and prognostication.Methods: This retrospective study analyzed clinicopathologic data, treatments and outcomes of 150 CRLM patients treated with NAC followed by liver resection at our hospital. The primary outcomes were progression-free survival (PFS) and overall survival (OS). The secondary outcome was postoperative major complications. The RDW level was presented as the RDW-SD level and the RDW-CV level. The optimal cut-off of RDW level was determined by X-tile analysis. The change in RDW was scored as 0 (decreased pre-NAC RDW and decreased preoperative RDW), 2 (elevated pre-NAC RDW and elevated preoperative RDW), or 1 (all other combinations). Multivariable logistic regression analysis was performed to determine the relationships between the tumour characteristics and pathological response and the postoperative major complications. A multivariate Cox proportional hazards model was used to evaluate the prognostic factors associated with survival.Results: The optimal cut-off values of the RDW-CV and RDW-SD levels for survival were 13.5% and 42.2 fl, respectively. The multivariate analysis showed that a preoperative RDW-CV ≥13.5% (OR =3.215, 95% CI: 1.299-7.958, P=0.012) significantly predicted a favorable pathological response. The multivariate analysis revealed that a pre-NAC RDW-CV ≥13.5% (OR =2.462, 95% CI: 1.080-5.615, P=0.032) significantly predicted postoperative major complications. In the multivariate analysis, an RDW-CV change =2 (HR =0.487, 95% CI: 0.309-0.768, P=0.002) was a significant predictor of better PFS. The multivariate analysis also revealed that an RDW-SD change =2 (HR =0.532, 95% CI: 0.332-0.854, P=0.009) were an independent predictor of better OS.Conclusions: This study revealed that pre-NAC RDW, preoperative RDW and RDW changes may be reliable markers that could predict a pathological response and prognosis in CRLM patients receiving NAC followed by liver resection.