Can a novel MRI staging system for low rectal cancer aid surgical planning?

BACKGROUND: Low rectal cancers are associated with worse outcomes in comparison with mid and upper rectal tumors. OBJECTIVE: This study aimed to assess the predictive accuracy of MRI in identifying the correct surgical approach based on the mesorectal and extralevator planes. DESIGN: This study involved the retrospective analysis of MRI and histopathology data of 33 patients with low rectal cancer, with the use of an anatomically based staging system. Three radiologists reported on the available surgical planes of excision based on the predicted relationship of tumor to key anatomical features. MRI-predicted planes of excision were then compared with the histopathological planes actually required, with the use of the same staging criteria. SETTINGS: The study was conducted at 4 English district general hospitals. PATIENTS: Unselected patients with low rectal cancer, all of whom were participants in a multicenter study, were eligible for this study. MAIN OUTCOME MEASURES: : The main outcome measured was the accuracy of operative plane prediction on MRI. RESULTS: : On pathological analysis, the mesorectal plane would have been sufficient to achieve a clear margin in 28 of 33 (84.9%) of cases. The extralevator plane was required in 5 of 33 (15.1%). Planes were correctly predicted by MRI in 29 of 33 cases by radiologist 1 and 24 of 33 cases by radiologists 2 and 3 with an accuracy of 87.9% and 72.7%. Overstaging (extralevator plane predicted when a mesorectal plane would have sufficed) occurred in 3 of 33 and 7 of 33 cases. Understaging (mesorectal plane predicted when an extralevator plane was required) occurred in 1 of 33 and 2 of 33 cases. The positive and negative predictive values of MRI in determining the histopathological plane of excision required were 57% and 96% for radiologist 1 and 30% and 91% for radiologists 2 and 3. LIMITATIONS: This study was limited by its retrospective nature and its relatively small patient numbers. No account was taken of postoperative function when recommending the surgical plane. CONCLUSIONS: This supports an anatomically based MRI staging system for low rectal cancer to predict the planes of surgical excision. This may help to reduce margin positivity and to improve outcome in patients with low rectal cancer.

MRI predictive factors for long-term outcomes of low rectal tumours.

BACKGROUND: Low rectal cancers have poor outcomes. It has been suggested that low tumours are biologically more aggressive and tend to be more locally advanced at presentation. Pre-operative identification of prognostic factors will enable use of selective neoadjuvant therapies and possibly increase sphincter-sparing rates where oncologically safe. METHODS: A subset of 101 patients with low rectal cancer (within 5 cm of the anal verge) in a multicentre trial were studied. MRI images were reviewed by a senior radiologist, blinded to outcome. MRI-predicted tumour spread and MRI tumour regression grade (TRG) were analysed for 5-year recurrence and survival rates using a Cox regression model. RESULTS: On univariate analysis, advanced MRI low rectal tumour stage correlated with greater incidence of recurrence (p=0.013) and death (p=0.029) compared with earlier stage tumours. Good MRI TRG score (good response to pre-operative therapy) correlated with significantly reduced tumour recurrence rates (p=0.008) and increased survival (p=0.008) versus the poor MRI TRG score group. On multivariate analysis, good MRI TRG score was associated with reduced recurrence (p=0.003) but not survival rates. CONCLUSIONS: This study confirms that MRI can be used to predict patients at increased risk of recurrence following surgery in low rectal cancer. This information can be used to direct pre-operative therapies and plan operative strategies. This is the first study to confirm the association between MRI TRG and long-term outcome. Poor response to neoadjuvant therapy can be used to plan use of further therapies prior to surgery to attempt to improve outcome.

Patients with low rectal cancer treated by abdominoperineal excision have worse tumors and higher involved margin rates compared with patients treated by anterior resection.

PURPOSE: Patients with low rectal cancer have worse outcomes compared to those with upper rectal cancer. Reports suggest that low anterior resection may be oncologically superior to abdominoperineal excision, although no good evidence exists to support this. We looked at a recent series of patients with low rectal cancer to explore some of the issues. METHODS: We analyzed 153 patients from the MERCURY study with low rectal cancer (

Defining the surgical planes on MRI improves surgery for cancer of the low rectum.

Cancer of the low rectum provides a challenge for both preoperative staging and optimum operative management. Current outcomes for patients with low rectal cancer are poor, particularly for those treated by abdominoperineal excision. It has been suggested that this poor outcome is due to an inherent oncological inferiority of the traditional abdominoperineal excision procedure, which might be explained by the unique anatomical features of the low rectum and the lack of clearly defined anatomical excision planes. In this Personal View, we discuss the anatomical and surgical planes available for the management of low rectal cancer, and describe the two-plane approach to low rectal cancer using the mesorectal plane and the extralevator plane.

MRI staging of low rectal cancer.

Low rectal tumours, especially those treated by abdominoperineal excision (APE), have a high rate of margin involvement when compared with tumours elsewhere in the rectum. Correct surgical management to minimise this rate of margin involvement is reliant on highly accurate imaging, which can be used to plan the planes of excision. In this article we describe the techniques for accurate magnetic resonance imaging (MRI) assessment and a novel staging system for low rectal tumours. Using this staging system it is possible for the radiologist to demonstrate accurately tumour-free planes for surgical excision of low rectal tumours.