Comparison of unenhanced and contrast-enhanced spiral CT for assessing interval change in patients with colorectal liver metastases

Rationale and Objectives. The purpose of this study was to determine whethe r the interval change in hepatic colorectal metastases as assessed with ser ial computed tomographic (CT) scans without contrast material enhancement d iffers from that as assessed using serial, portal dominant phase, contrast- enhanced CT scans. Materials and Methods. Unenhanced and contrast-enhanced abdominal CT scans were obtained in 28 patients. Three radiologists separately reviewed serial unenhanced and contrast-enhanced studies to assess the interval change in liver metastases. These radiologists recorded total number of lesions, bidi mensional measurements of the largest lesions (as many as three), and overa ll impressions regarding the interval change (none, worse, or better). Results. Among the 84 judgments (28 patients x 3 radiologists), comparisons of unenhanced and contrast-enhanced CT studies were concordant in 60 asses sments (71%). Nineteen (23%) showed mild disagreement. Of these, contrast-e nhanced CT studies demonstrated disease stability when unenhanced CT studie s demonstrated otherwise in 11 judgments, whereas unenhanced CT studies dem onstrated stability when contrast-enhanced CT studies demonstrated otherwis e in eight assessments. Furthermore, of the five marked disagreements, two resulted from a conclusion of interval improvement on unenhanced CT studies and a conclusion of interval worsening on contrast-enhanced CT studies, wh ereas three demonstrated the opposite. Neither set of serial CT studies sys tematically resulted in under- or overestimation of disease progression (Mc Nemar Q test, P < .25). Conclusion. The authors found no consistent pattern to demonstrate that ser ial unenhanced or contrast-enhanced CT studies resulted in over- or underes timation of disease progression.