Preoperative knowledge of tumor stage and of the threatened circumferential resection margin (CRM) are essential for planning the surgical procedure and as predictors of local recurrence of rectal cancer.
At present most units utilize CT scanning to assess these parameters.
Doctors at the West Middlesex University Hospital, UK, examined the accuracy of preoperative CT and MRI staging of rectal cancers compared with final histology.
They also assessed the accuracy of MRI in predicting penetration of the mesorectal envelope.
47 patients with biopsy proven rectal adenocarcinoma underwent preoperative MRI and CT scan.
CT correctly staged 77% of patients with T1 or T2 stage rectal tumors compared with only 43% accuracy for MRI.
| There are significant differences between the accuracy of preoperative 'T' staging by CT and MRI |
Conversely, MRI correctly staged 73% of patients with T3 rectal tumors compared to 41% accuracy with CT scanning.
CT and MRI staged T4 disease with equal accuracy.
In the assessment of mesorectal envelope integrity, the research team showed that MRI had a sensitivity of 80% and a specificity of 84%.
The research team conclude, “MRI has the potential to accurately assess mesorectal envelope invasion”
However, “Further analysis is required to assess whether MRI can be used as the sole modality in preoperative staging of rectal cancers.”