Diagnostic accuracy of preoperative magnetic resonance imaging in predicting curative resection of rectal cancer: prospective observational study

Abstract

Objective To assess the accuracy of preoperative staging of rectal cancer with magnetic resonance imaging to predict surgical circumferential resection margins. Design Prospective observational study of rectal cancers treated by colorectal multidisciplinary teams between January 2002 and October 2003. Setting 11 colorectal units in four European countries. Participants 408 consecutive patients presenting with all stages of rectal cancer and undergoing magnetic resonance imaging before total mesorectal excision surgery and histopathological assessment of the surgical specimen. Main outcome measures Accuracy of magnetic resonance imaging in predicting a curative resection based on the histological yardstick of presence or absence of tumour at the margins of the specimen. Results 354 of the 408 patients had a clear circumferential resection margin (87%, 95% confidence interval 83% to 90%). Specificity for prediction of a clear margin by magnetic resonance imaging was 92% (327/354, 90% to 95%). High resolution scans were technically satisfactory in 93% (379/408). Surgical specimens were histopathologically graded as complete or moderate in 80% (328/408), and the median lymph node harvest was 12 (range 0-49). Magnetic resonance imaging predicted clear margins in 349 patients. At surgery 327 had clear margins (94%, 91% to 96%). Conclusion High resolution magnetic resonance imaging accurately predicts whether the surgical resection margins will be clear or affected by tumour. This technique can be reproduced accurately in multiple centres to predict curative resection and warns the multidisciplinary team of potential failure of surgery, thus enabling selection of patients for preoperative treatment. IntroductionColorectal cancer is a common malignancy and the second commonest cause of cancer death in the Western world. Rectal cancer, defined as a tumour with its lower edge within 15 cm from the anal verge, accounts for about a third of all colorectal malignancies. Management is particularly challenging technically for the surgeon and local recurrence within the pelvis is a common result of treatment failure. In total mesorectal excision surgery, the plane of dissection is formed by the mesorectal fascia, which encloses the fatty mesorectum that envelops the rectum. This fascia forms the circumferential resection margin, and tumour within 1 mm of the potential circumferential resection margin (the radial margins of the surgical resection specimen) strongly predicts local recurrence and poor survival.2 3 While the optimal surgical technique of total mesorectal excision can cure early stage localised rectal cancer, 3 4 it is now evident that preoperative radiotherapy or chemoradiotherapy 5 may facilitate successful surgical excision and therefore improve outcome in patients with more extensive disease. Previous studies have found high rates of tumour in the circumferential resection margins; 22-27% in recent studies. [6][7][8] Therefore, the optimal management of rectal cancer requires detailed preoperative planni...

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