PET/CT provides colorectal tumor information in one step

Raquel Harper

Colorectal cancer is the fourth most common cancer found in both men and women. For an effective therapy approach, clinicians need to know the exact and complete staging of the tumor.

Optical colonoscopy is currently the detection reference standard, although it provides only endoluminal images. Additional imaging procedures, such as CT followed by PET, are needed to assess a tumor’s spread to lymph nodes and solid organs to diagnose its stage. However, the multistep approach can be time-consuming, and patients often feel overwhelmed with the number of imaging procedures that are required to get a complete diagnosis.

Dr. Gerald Antoch from University Hospital Essen in Essen, Germany, and his colleagues investigated the staging accuracy of whole-body PET/CT colonography compared with the staging accuracies of CT followed by PET (CT + PET) and CT alone to see if the single-step PET/CT would be an accurate and less time-consuming approach for diagnosing the disease.

CT provides information only about the physical shape and size of the tumor, but not on how the tumor is functioning. PET provides functional data, but because of its limited spatial resolution, exact anatomic localization of lesions is difficult. Therefore, both are helpful for detecting and characterizing malignant lesions.

The researchers tested 47 patients with a total of 50 lesions (which were initially detected by colonoscopy with biopsy) with a PET/CT system from Siemens AG of Germany. In these patients, the overall TNM stage (each letter stands for a different classification of tumor stage) was correctly determined for 37 lesions with PET/CT colonography, for 32 lesions with CT followed by PET and for 26 lesions with CT alone.

The researchers believe that their results prove that PET/CT colonography is at least equivalent in accuracy to CT followed by PET and is perhaps a more efficient and less burdensome approach for determining complete tumor staging in colorectal cancer patients.

JAMA, Dec. 6, 2006, pp. 2590-2600.