Measurement of K, Fe, Cu and Zn levels in secondary colorectal liver cancer and surrounding normal liver tissue, and their potential as a tissue classifier

An x-ray fluorescence (XRF) system utilising a synchrotron radiation source was used to quantify the levels of Fe, Cu, Zn and K in colorectal liver metastases and surrounding normal liver tissue as a possible mechanism for detecting cancer in a tissue biopsy. Sixty samples were measured and a lower level of all four elements was found in the cancer samples compared with that of the normal liver. The difference in levels of Zn, Fe, Cu and K between cancer and normal tissue was significant with p values of <0.01 for Zn, Fe and K, and 0.033 for Cu. The precision was estimated by repeated measurements yielding a precision of 96,91, 95 and 86% for Zn, Cu, Fe and K, respectively. The homogeneity of the distribution of elemental concentrations was assessed by measuring eight normal liver and eight cancer samples from the same patient. The variation of Zn, Cu, Fe and K levels between normal liver samples was 10.4, 15.4, 15.85 and 29.1%, respectively, and in the colorectal metastases was 10.18, 15.92, 8.44 and 22.35%, respectively. Receiver operator characteristic (ROC) analysis was performed for all elements and showed that Zn could be a reliable indicator of tissue classification with an ROC area under the curve of 0.998 and a resulting sensitivity and specificity of 100 and 96.67%, respectively. Fe had an ROC area under the curve of 0.856 and sensitivity and specificity of 83.3 and 76.67%, respectively. Cu and K did not perform as well with areas under the curve of 0.75 and 0.706, respectively. Copyright (C) 2008 John Wiley & Sons, Ltd.