Whole-body Scans May Provide Option For Diagnosing Colorectal Cancer

Colorectal cancer accounts for a large number of tumor-related deaths. Exact and complete information on the stage of the tumor is of great benefit to patients, according to background information in the article. Determining the stage of colorectal cancer often requires a multimodality, multistep imaging approach. Complete "conventional" staging determination requires additional imaging procedures to assess potential metastatic spread to lymph nodes and solid organs. Colonography combining the imaging procedures of positron emission tomography (PET) and computed tomography (CT) provides whole-body tumor staging in a single session.

Of conventional imaging procedures, contrast-enhanced CT is the most common for both the abdomen and the thorax. However, CT offers only form and structure data for the evaluation of the tumor stage. Combined PET/CT scanners have been introduced into clinical practice to provide additional information on a tumor. By performing PET/CT colonography as a whole-body imaging procedure, multimodality diagnostic workup can be shortened.

Patrick Veit-Haibach, M.D., of University Hospital Essen, Germany, and colleagues evaluated the diagnostic accuracy of whole-body PET/CT colonography for 47 patients with colorectal cancer and compared those findings with the accuracy of conventional CT staging alone and CT followed by PET (CT + PET). Patients with clinical findings and optical colonoscopy that suggested primary colorectal cancer were enrolled between May 2004 and June 2006. Patients underwent whole-body PET/CT colonography 1 day after colonoscopy. Fifty lesions were detected in the 47 patients.

Based on a lesion-to-lesion analysis, TNM stage (different classifications of tumor stage) was correctly determined by PET/CT colonography in 37 (74 percent) of 50 lesions and by CT alone in 26 (52 percent) of 50 lesions at a certain threshold of measurement. With CT + PET, TNM was correctly determined in 32 (64 percent) of 50 lesions. Compared with optimized abdominal CT staging alone, PET/CT colonography was more accurate in defining TNM stage (difference, 22 percent), which was mainly based on a more accurate definition of the T-stage.

Of the 47 patients, PET/CT colonography changed the therapy management in 4 (9 percent) compared with conventional staging. The change in patient management was based either on a more accurate assessment of the tumor stage of colorectal cancer or on accompanying findings on PET/CT colonography.

"In addition to optical colonoscopy, whole-body PET/CT colonography as an all-in-one staging modality seems feasible to provide an alternative to the multimodality, multistep staging in patients with colorectal cancer. ... It is less time-consuming than a conventional multistep approach with CT alone (abdomen and thorax) and PET imaging if required. Thus, it represents a psychological and physical advantage when considering the burden to the patient of different imaging procedures. The referring physician will receive a single report including complete tumor staging in a single step, enabling him/her to define further therapy," the authors write.

"This preliminary report suggests that PET/CT colonography may be at least equivalent to CT + PET with respect to tumor staging in patients with colorectal cancer. The reason for a change in patient management with PET/CT colonography compared with a conventional staging concept must be attributed partially to the detection of synchronous [existing at the same time] tumors rather than to a more accurate TNM staging of colorectal cancer. Because an all-in-one staging modality has to offer both accurate TNM staging of the tumor in question and information on potentially present synchronous tumors, PET/CT colonography in conjunction with optical colonoscopy may be suitable for whole-body all-in-one tumor staging in patients with colorectal cancer," the researchers conclude.