Pulmonary staging in colorectal cancer--is computerised tomography the answer?

Pulmonary staging in colorectal cancer (CRC) has traditionally been carried out by means of plain chest radiograph (CXR), although computerised tomography (CT) imaging of the chest is increasingly being performed for this purpose. The aim of this study was to assess the value of pre-operative thoracic CT for pulmonary staging in CRC.

Data were collected prospectively on all patients referred into hospital over a 20-month study period for double contrast barium enema evaluation of symptoms suggestive of an underlying CRC. Patients with a CRC went on to have a staging intravenous, contrast-enhanced CT of the chest, abdomen and pelvis prior to an out-patient appointment with a colorectal surgeon. The CXRs of those patients in whom a radiological abnormality was seen on thoracic CT were reviewed blindly by an independent consultant radiologist.

A total of 403 barium enemas were performed, of which 38 demonstrated a CRC (9%). In those patients diagnosed with CRC, nine (24%) had an abnormality on thoracic CT. Four patients with positive thoracic CTs had chemotherapy and or radiotherapy with no surgery. One patient underwent colectomy, and 2 patients who had primary lung tumours as opposed to metastases also underwent colectomies. One patient received palliative care only. In addition, one of the patients underwent multiple, non-diagnostic thoracic investigations prior to a diagnosis of sarcoidosis being made and then proceeding to surgery. An independent consultant radiologist reviewed seven out of the nine CXRs of patients with an abnormality on thoracic CT without knowledge of the clinical diagnosis, and reported three of the CXRs to be normal.

Thoracic CT appears to improve the accuracy of pulmonary staging in CRC allowing a more appropriate level of intervention. However, CT is likely to identify more benign radiological abnormalities than CXR alone, and investigations should not occur to the detriment of treating the primary tumour.