Cancer biomarkers are biological, chemical or biophysical entities that are present in tumor tissues or body fluids which give valuable information about current and future behavior of cancer. This review discusses the applicability of biomarkers in different stages of cancer from cancer risk assessment to recurrence. In medical practice, biomarkers can be helpful in finding out one's potential cancer risk, confirming whether or not one is already affected with a particular type of cancer, to which drug will the cancer respond best and in what doses should it be administered, the effectiveness of the treatment and whether the cancer will recur. Although biomarker discovery and validation is a very challenging process, when considering its applications and advantages, it is well worth the effort.