FDG-PET and Tumour Marker Tests for the Diagnosis of Breast Cancer

Abstract

Circulating tumour markers for breast cancer can be classified in different groups: mucins such as CA 15.3, CA 27.29 and CA 549, carcinoembryonic antigen (CEA), cytokeratins (TPA, TPs, Cyfra 21.1), enzymes (LDH), hormones and their subunits. All of them have been proposed over the years for the diagnosis and monitoring of breast cancer at different stages. It is well known that tumour marker tests lack in sensitivity at the earliest stage of cancer and also in specificity. False-negative results are rare in patients with advanced disease and metastases; on the contrary they are most frequent in the first stages. Besides this, false-positive results can be due to different nonmalignant conditions. At present CA 15.3 is the most widely used tumour marker in breast cancer patients. Its use follows the general concepts everywhere accepted for mucinic markers: the CA 15.3 test is not useful in screening and early diagnosis; it has an established role in the diagnosis of recurrences; it has an established role in therapy monitoring, alone or in association with other diagnostic tools; it is still under study as a predictor of response to therapy. Several international guidelines help physicians in using tumour markers giving practical recommendations for the appropriate interpretation of circulating tumour markers. CEA and cytokeratins markers are so far less specific than mucinic markers; therefore, they are sometimes tested for evaluating breast cancer patients.