Magnetic resonance imaging performed before and after preoperative chemoradiotherapy in rectal cancer: predictive factors of recurrence and prognostic significance of MR-detected extramural venous invasion

Purpose To evaluate the role of magnetic resonance imaging (MRI) performed before and after neoadjuvant chemoradiotherapy (nCRT) in predicting risk of recurrence in rectal cancer and to investigate the prognostic significance of MR-detected extramural venous invasion (mr-EMVI) and of its regression after nCRT. Methods During 2005-2016, 87 patients with rectal cancer underwent pre- and post-nCRT MRI before surgery. Two radiologists independently reviewed MR examinations retrospectively, assessing T stage, nodal involvement, circumferential resection margin (CRM) status, and mr-EMVI. All four parameters assessed in pre- and post-nCRT MRI were correlated with the risk of recurrence. Correlation with disease-free survival (DFS) was investigated for significant predictive factors in pre-nCRT MRI and for mr-EMVI and its possible regression in post-nCRT MRI. Results 15 of 87 patients developed recurrence, with a relapse-rate of 17.2%. Statistical analysis showed a significant correlation between CRM involvement and mr-EMVI assessed in pre-nCRT MRI and the risk of recurrence; 3 years-DFS in patients positive for these two parameters was significantly shorter compared with negatives. In post-nCRT MRI, all four parameters correlated significantly with recurrence: mr-EMVI affected significantly 3 years-DFS and its regression after nCRT correlated with a trend toward improvement of survival outcomes, although not statistically significant. Conclusions CRM involvement and mr-EMVI assessed in pre-nCRT MRI should be considered early predictive factors of recurrence in rectal cancer. MRI performed after nCRT has a significant value in predicting risk of recurrence: mr-EMVI confirmed to be a poor prognosis predictor and its regression or persistence after nCRT could have influences on treatment and follow-up strategies.