Significance of MRI in rectal carcinoma therapy optimization - correlation of preoperative T- and N-staging with definitive histopathological findings

In past decades, both prognosis and therapy of rectal cancer patients showed significant improvement, on the other hand, the incidence of rectal carcinoma continues to have a rising tendency. According to current UICC classification, patients in stage II rectal cancer or higher are indicated for neoadjuvant chemoradiotherapy (nCRT). Magnetic resonance imaging (MRI) is currently the most common diagnostic method used for preoperative staging of rectal cancer. Several studies already pointed out the inaccuracy of preoperative lymph node staging in patients with rectal cancer. The present study analyzed overall accuracy of MRI staging of rectal cancer and thus its accuracy in neoadjuvant therapy indication, by comparing preoperative MRI staging with definitive histopathologic results from resected tumors. This study evaluated cases of 92 patients with rectal tumor that underwent MRI examination followed by surgical resection. Tumors included in the analysis were ranging from T1 to T3b according to TNM staging, with free circumferential resection margin (CRM), distance form mesorectal fascia more than 5 mm, negative intersphincteric plane and also negative extramural venous invasion (EMVI), while the N stage was not decisive. In all cases both N-staging and T-staging were evaluated histologically and compared with preoperative MRI results. Significant difference in preoperative and postoperative N-staging was shown in 51 patients (61.45%). In majority of cases MRI lead to overstaging, which was observed in 44 cases (53.1 %), with complete negativity of lymph nodes proven by histological examination in 34 cases. On the other hand, understaging of lymph nodes was observed only in 7 cases (7.4 %). The T-staging did not show significant differences. Results from this study confirm that MRI plays an important role in T-staging of rectal tumors, however, there are admittedly issues in N-staging of tumors, which should lead to reevaluation of neoadjuvant therapy indication in patients with positive lymph nodes according to MRI examination. Based on the results of this study, we see the future of preoperative staging of rectal tumors in precise T-staging together with accurate assessment of CRM and distance of tumor from mesorectal fascia as well as evaluation of intersphinteric plane and EMVI.