Contrast-enhanced CT scanning of the chest, abdomen, and pelvis is the preferred study for preoperative staging of patients with newly diagnosed colorectal cancer. This provides the most reliable means of detecting the presence of metastatic disease to the lungs, liver, intra-abdominal lymph nodes, and peritoneum, which are the most common sites of metastatic spread, and is useful in planning appropriate therapy.
A bone scan is not indicated at this time. Although bone metastases may be present in patients with several other types of cancer at presentation, this finding is extremely rare in patients with newly diagnosed colorectal cancer. Up to 10% of patients with colorectal cancer may develop bone metastases as a late complication of advanced metastatic disease, but evaluation at the time of diagnosis in the absence of specific and compelling symptoms is not warranted.
CT colonography appears to be an acceptable alternative to colonoscopy for screening of otherwise low-risk healthy individuals; however, this study is not part of the staging work-up for a patient with a known cancer diagnosis.
PET/CT scans have not been shown to improve the accuracy of preoperative staging for patients with colorectal cancer and are not recommended for either preoperative staging or postoperative surveillance.