Synopsis

In order to tapped the potential of pCR prediction on T2WI comprehensively, both quantitative and qualitative parameters were evaluated in patients with locally advanced rectal cancer. A development group were enrolled to assess these parameters and an external validation group to verify the diagnostic performance. Post-nCRT CATV (CATVpost) and the reduction rate of SIT (SITRR) were proved that were independently associated with pCR and can help for pCR prediction.

Introduction

There has been a gradual shift from radical surgery following neoadjuvant chemoradiotherapy(nCRT) to “wait-and-see” strategy for patients with pathological complete response (pCR) in locally advanced rectal cancer(LARC), however, identifying patients with pCR using a noninvasive test currently is a challenge. This study aim to investigate the effective quantitative and qualitative parameters on T2-weighted magnetic resonance imaging (MRI) for predicting pCR in patients with LARC.

Methods

Eighty-four consecutive patients were enrolled who had undergone pre- and post-CRT MRI. Quantitative parameters including maximum tumor length(MTL), maximum tumor area(MTA), cylindrical approximated tumor volume(CATV) and signal intensity (SIT) were measured, the reduction rate of them were calculated, and the tumor regression grade on MRI(MR-TRG) and conventional MRI features also were evaluated. A multivariate logistic regression analysis was performed to analysis the effective parameters for predicting pCR before surgery. An external cohort of 36 patients as a validation group to verify the pCR prediction protocol. And receiver operating characteristic (ROC) analysis was used to assess the diagnostic performance of developmentand validation group.

Results

In development and validation group, there were 16 patients (19.0%) and 12 patients (33.3%) achieved pCR respectively. On multivariate analysis, post-nCRT CATV (CATVpost: OR, 0.61; p=0.007) and the reduction rate of SIT (SITRR: OR, 51.16; p=0.012) were independently associated with pCR. The area under the receiver-operating characteristic curve (AUC) for predicting pCR in development group is 0.875(sensitivity 0.813, specificity 0.838) versus in validation group is 0.865(sensitivity0.750, specificity 0.875).

Discussion

Several studies have proven tumor volume measured on T2WI have high diagnostic performance for predicting pCR while another reported tumor signal intensityis good, and one study confirmed that MR-TRG may help. Both of them considered respectively. In our study, all of these parameters were considered comprehensively. Overall, quantitative parameters show more advantages for predicting pCR than qualitative parameters, which may due to poor interreader agreement of qualitative parameters.The AUC of validation group was similar to development group, but lower sensitivity, which may was limited by a small sample size.

Conclusion

Acknowledgements

References

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