Prognostic value of preoperative magnetic resonance imaging of the pelvis in rectal cancer

Background: Despite radiotherapy and improved surgical techniques, local recurrence rates after treatment of rectal cancer still vary between 3 and 30 percent. Tumour involvement of the circumferential resection margin (CRM) predicts a high risk of local recurrence. Magnetic resonance imaging (MRI) allows accurate description of the turnout and its spread within the mesorectum. The aim of this study was to assess the prognostic impact of an involved CRM identified at preoperative MRI in patients with rectal cancer. Methods: Preoperative MRI was performed in 115 patients with rectal cancer between 1995 and 1999. The images were evaluated retrospectively. The shortest distance from the tumour to the CRM was measured, correlated with patient outcome and compared with histopathological findings. Results: The risk of any recurrence in patients with or without a tumour-involved margin on MRI was nine of 29 and nine of 57 respectively (P = 0.036). Overall survival at 5 years was 43 and 77 per cent (P = 0.012) respectively. Twenty-four of 30 patients who had an involved CRM on histopathology were correctly identified by MRI. Conclusion: Patients with a potentially involved CRM identified by MRI had a significantly higher risk of recurrence and cancer-related death. Preoperative MRI may be of prognostic value in rectal cancer and may be used to select patients for neoadjuvant radiochemotherapy and/or more radical surgery.