Prediction of pathological prognostic factors of rectal cancer by relaxation maps from synthetic magnetic resonance imaging

Purpose: To explore the feasibility of relaxation maps from synthetic MRI for predicting pathological prognostic factors of rectal cancer (RC) and to compare the predictive performance of quantitative values and conventional subjective evaluation. Material and methods: A total of 94 patients with pathologically proven RC who underwent direct surgical resection were enrolled in this prospective study. Preoperative rectal MRI including synthetic MRI was performed. The mean T1, T2, and PD value of the whole tumor was obtained to preoperatively assess the pathological T stage, N stage, extramural venous invasion (EMVI), differentiation, and perineural invasion. Receiver operating characteristic curves were used to explore the predictive performance for assessing the prognostic factors. The T stage, N stage and EMVI status on conventional T2WI were evaluated and compared with the quantitative values. Results: The T2 value decreased significantly in patients with positive perineural invasion, lymph node metastasis (LNM), EMVI, and higher T stage RC (p = 0.007 and < 0.001). The T1 value of LNM and EMVI positive groups was significantly lower than those of the negative groups (p = 0.034 and 0.011). For predicting N stage and EMVI, the T2 value demonstrated good performance with an AUC of 0.883 (95 % confidence interval, CI, 0.801-0.940) and 0.821 (95 % CI, 0.729-0.893); the T2 value was superior to the T1 value and subjective evaluation of radiologists (all p < 0.05). Conclusion: Synthetic MRI is a promising tool for noninvasive evaluation of prognostic factors of RC by generating relaxation maps.

Automated summary

The study indicates that relaxation maps from synthetic MRI may be feasible for predicting pathological prognostic factors in rectal cancer patients. Quantitative values show good performance in predicting N stage and EMVI, surpassing traditional subjective evaluations.