Tumor markers in clinical practice: a review focusing on common solid cancers.

Tumor markers are playing an increasingly important role in cancer detection and management. These laboratory-based tests are potentially useful in screening for early malignancy, aiding cancer diagnosis, determining prognosis, surveillance following curative surgery for cancer, up front predicting drug response or resistance, and monitoring therapy in advanced disease. Clinically useful markers include fecal occult blood testing in screening for early colorectal cancer, carcinoembryonic antigen in the management of patients with colorectal cancer, both α-fetoprotein and human chorionic gonadotrophin in the management of patients with non-seminomatous germ cell tumors, CA 125 for monitoring therapy in patients with ovarian cancer, estrogen receptors for predicting response to hormone therapy in breast cancer, human epidermal growth factor receptor 2 for the identification of women with breast cancer likely to respond to trastuzumab (Herceptin) and KRAS mutational status for identifying patients with advanced colorectal cancer likely to benefit from treatment with the anti-epidermal growth factor receptor antibodies, cetuximab and panitumumab. Although widely used, the value of prostate-specific antigen screening in reducing mortality from prostate cancer is unclear.