Postgraduate Medical Institute, Lahore General Hospital
Abstract
The amount of published literature on biomarkers has exponentially increased
over the last two decades. Cancer biomarkers are molecules that are either part
of tumour cells or secreted by tumour cells. Biomarkers can be used for diagnosing
cancer (tumour versus normal and differentiation of subtypes), prognosticating
patients (progression free survival and overall survival) and predicting
response to therapy. However, very few biomarkers are currently used in clinical
practice compared to the unprecedented discovery rate. Some of the examples
are: carcino-embryonic antigen (CEA) for colon cancer; prostate specific antigen
(PSA) for prostate; and estrogen receptor (ER), progesterone receptor (PR) and
HER2 for breast cancer.
Cancer biomarkers passes through a series of phases before they are used in
clinical practice. First phase in biomarker development is identification of biomarkers
which involve discovery, demonstration and qualification. This is followed
by validation phase, which includes verification, prioritisation and initial
validation. More large-scale and outcome-oriented validation studies expedite
the clinical translation of biomarkers by providing a strong ‘evidence base’. The
final phase in biomarker development is the routine clinical use of biomarker.
In summary, careful identification of biomarkers and then validation in well-designed
retrospective and prospective studies is a systematic strategy for developing
clinically useful biomarkers
