Could preoperative MRI predict rectal cancer outcomes?

This study evaluated preoperative magnetic resonance imaging (MRI) in the evaluation of surgical margins among rectal cancer patients.

Surgical removal of the tumor is the optimal treatment in the case of local rectal cancer. Removal of the intact tumor, with surrounding tissue and lymph-nodes, without leaving behind any residual cancer cells, is crucial for treatment success and the prevention of cancer recurrence. The ability to perform this complete resection depends greatly on tumor location and size. The proximity of the tumor edge to a structure called the mesorectal fascia is known to influence surgery outcome and the risk of cancer recurrence. Tumors within one millimeter of the mesorectal fascia, referred to as having a positive or involved resection margin, are known to predict both local recurrence and poor survival.

Currently, preoperative treatments such as radiotherapy, are offered to patients mainly according to cancer stage. Multiple imaging techniques have shown acceptable accuracy for assessing tumor stage and lymph node involvement, however only MRI allows for the accurate assessment of potential resection margins. The ability to further predict recurrence risk before surgery according to MRI resection margins should enable better selection of preoperative treatments, in addition to providing a surgical roadmap to avoid breaching the tumor.

A total of 374 patients diagnosed with stage I-III rectal cancer, and planned to undergo surgery, were assessed by MRI. The rate of cancer progression, local recurrence and overall survival was analyzed 5-years following surgery according to MRI predicted resection margins.

98 (26%) of 374 patients were considered to have potentially involved resection margins according to preoperative MRI. The risk of positive surgical margins (tumor cells along the line of surgical excision, indicating residual tumor cells left within the body) was 17-times higher among patients with MRI-predicted involved resection margins. Cancer outcomes were also found to be directly associated with MRI-predicted resection margins. The estimated 5-year overall survival rate was 62.2% among patients with predicted clear resection margins, compared to 42.2% among patients with predicted positive resection margins. 67.2% of patients with predicted clear margins survived without progression of their disease for at least 5 years, compared to 47.3% of patients with predicted positive margins. In addition, the rate of local recurrence was significantly reduced among patients with MRI-predicted clear resection margins. Only 7.1% of patients with predicted clear margins experienced local cancer recurrence, compared to 20% of patients with predicted involved resection margins.

This study concluded that among rectal cancer patients, preoperative magnetic resonance imaging is a good predictor of surgical margins, disease progression, local recurrence and overall survival.