CT of Colon Cancer Metastases to the Liver Using Modified RECIST Criteria: Determining the Ideal Number of Target Lesions to Measure

Abstract

We sought to define the ideal number of target lesions to be measured to assess disease response in patients undergoing chemotherapy for colon cancer metastases to the liver. Thirty consecutive patients were recruited for this study. Patients were part of a multisite, randomized, double-arm, phase 3 clinical trial involving chemotherapy with an investigational drug for metastatic colon cancer. Patients were recruited from U.S. and international sites. Institutional review board approval was obtained, and informed consent was obtained from all patients. Our study included CT measurements of hepatic metastases. All patients (n = 30) had a minimum of five target lesions in the liver. Target-lesion size was defined by Response Evaluation Criteria in Solid Tumors (RECIST) criteria. We calculated the patient response at 2 months and at 6 months (complete response, partial response, stable disease, and progressive disease) using RECIST. Patient response was calculated based on the percentage increase or decrease at 2 and 6 months in the greatest diameter of the single largest lesion, two large lesions, three large lesions, four lesions, and five lesions, respectively. The concordance between five-target-lesion measurement and lesser numbers of lesions was analyzed using kappa statistics (StatView, 5.0). In 93.33% of patients (n = 28/30), there was agreement on patient response irrespective of the number of measurements made on CT. Of these 30 patients, 47% had a partial response (n = 14/30), 43% had stable disease (n = 13/30), and 10% had progressive disease at 2 months (n = 3/30). At 6 months, 43% had a partial response (n = 13/30), 47% had stable disease (n = 14/30), and 10% had progressive disease (n = 3/30). Agreement in response evaluation between lesion groups for multiple measurements was high, with values of 1.0 for multiple-lesion measurements and 0.88 for single-lesion measurements at 2 months. The concordance values were the same at 6 months. In the majority of patients with hepatic metastases of colorectal cancer, measuring the maximal diameter of the single largest lesion yielded the same treatment-response classification as measuring up to five target lesions. This result suggests that it may be possible to reduce the number of lesions measured in clinical trials.