Current trends in cancer biomarkers

Because of the severity of the group of diseases known as cancer nearly 80% of the Pharmaceutical Industry are developing and trial testing new cancer drugs. An increasing number of potential drug targets particularly to tumor cells continue to be discovered and studied There are more than four thousand genes and gene products, which are implicated in the biology of cancer. However, the critical parameters remain to be those of specificity and sensitivity of a test, which can simply identify ideally which patients will respond to a drug regardless of treatment status.

Tumor marker antigens have been in clinical use since the 1970s. The carcinoembryonic antigen (CEA) blood test used to monitor colon cancer reoccurrence was first approved by the FDA in 1973. Yet, in the thirty plus years since then there have been only about a dozen of such FDA approved similarly used markers being used in clinical practice. The problem with these tumor marker blood tests are that they are only about 80% specific and even less sensitive with regard to recurrence detection of disease.

During the past decade genetic tests, primarily PCR based, have been introduced into clinical diagnostics. There are at least four gene set FDA approved tests using biopsy tissue, which help physicians assess patient risk for the recurrence of breast cancer. They help to determine the need for chemotherapy in hormone or Estrogen receptor positive, node negative breast cancer patients with small tumors. The problem with these tests is that there is a large grey zone result, which does not help the physical and patient to decide to use the chemotherapeutic drug, or not. In addition these tests are for the primary tumor and may not reflect the metastatic condition or potential of the patient.

Today biopharma/pharma companies are performing clinical trials using a very practical test method for detection of disease recurrence and for efficacy of treatment, which can reflect the metastatic status of a patient's cancer. Circulating Tumor Cells (CTC's) in the blood of a post treatment patient has the potential to detect quantitatively the recurrence of a cancer which has been refractory for the treatment .In addition, by testing the captured cells for specific surface markers and for DNA/RNA an appropriate and specific salvage drug therapy may be identified. An FDA approved automated system for capturing and accurately identifying CRCs has enabled this important cancer biomarker tool to now be clinically viable. Prior to this technological improvement twenty years of work with CRCs as biomarkers did not meet clinical diagnostic standards. Also, PCR technologies are automated and reagents improved as compared to those of a decade ago leading to more reliable and effective results. Fortunately the technologies for measuring proteins, DNA, and tumor cells are all mature and robust allowing for expanded applications. The. Biopharmaceutical Industry is moving rapidly using these technologies. Correlating quantitation of cells with cancer disease recurrence has been done and is understandable and sensible to physicians and patients. If a patient is being treated with a drug and tumor cells still appear in the blood then the treatment may be ineffective. The future potential of CTC's is to be able to identify the genes and gene products which can then help identify effective and timely treatment which is often critical toward the survival of the patient.