Preoperative staging of rectal cancer: pelvic MRI plus abdomen and pelvic CT. Does extrahepatic abdomen imaging matter? A case for routine thoracic CT.

OBJECTIVE: To assess the quality of preoperative magnetic resonance imaging (MRI) staging of rectal cancer, and the clinical significance of abdomen and pelvic computed tomogram (CT) scans in preoperative staging of rectal cancer in a district general hospital. We postulated that the 'metastatic yield' of extrahepatic abdominal imaging is poor, and rarely altered management of rectal cancer.
METHODS: This is a retrospective study of preoperative MRI, CT scans and postoperative histology results of patients who had definitive surgery for rectal cancer at the Mid-Staffordshire General Hospitals NHS Trust over a 36-month period. Preoperative multiplanar pelvic MRI locoregional staging was compared with eventual histology. The incidence of and significance of abdomen and pelvic CT detected pathology (including metastasis) in the management of rectal cancers was also assessed.
RESULTS: Preoperative pelvic MRI correctly predicted 'clear' Circumferential resection margins, in 28 of 29 patients who had primary surgery. This is comparable with many published studies. Significant CT detected pathology (including metastasis) on preoperative abdomen and pelvic CT scans was uncommon, and did not influence management of any rectal cancer patient in our study. DISCUSSION: Given that exclusive CT detected significant pathology caudal to the liver (extrahepatic abdomen) is rare, can full abdomen and pelvic CT scans be justified for preoperative staging of rectal cancers? - especially where chest X rays are employed for lung staging. Preoperative thoracic and upper abdomen CT scan may be a more productive use of resources. Full abdominal scans may be more appropriate for selection of rectal cancer patients with isolated liver metastasis for metastasectomy.