Dynamic contrast-enhanced MRI to evaluate the therapeutic response to neoadjuvant chemoradiation therapy in locally advanced rectal cancer

Purpose To evaluate the usefulness of perfusion parameters derived from dynamic contrast-enhanced MR imaging (DCE-MRI) for assessing the therapeutic response to neoadjuvant chemoradiation therapy (CRT) for locally advanced rectal cancer (LARC). Materials and Methods Fifty patients with LARC (≥T3 or lymph-node metastasis) who underwent CRT and subsequent surgery, were included in this study. All patients underwent pre- and post-CRT DCE-MRI on a 1.5 Tesla unit. By using a postprocessing software, the following perfusion parameters (K^trans, k_ep, v_e) were measured for tumor. Those perfusion parameters were compared not only between the T-downstaged group and the nondownstaged group, but also before and after CRT in each group. Results After CRT, the mean K^trans (min^-1) significantly decreased from 1.24 ± 0.53 to 0.76 ± 0.45 in the T-downstaged group (n = 24) (P = 0.0007), whereas it did not significantly decrease in the nondownstaged group (n = 26) (from 1.02 ± 0.53 to 0.87 ± 0.48, P = 0.24). The percentage difference between pre- and post-CRT K^trans in the T-downstaged group was significantly higher than that in the nondownstaged group (43%, 16%, respectively, P = 0.0092). However, none of the other parameters showed significant differences. Conclusion A large decrease in the mean K^trans after CRT was associated with a good therapeutic response to CRT for LARC.