In cancer, often questions arise, “which tumor type is this, will the treatment benefit?” Scientists answer such questions by measuring biomarkers in blood, urine, sputum or biopsy (removal of tumor sample).
Biomarkers play an important role in answering number of questions, covering
- Diagnostic: What type of cancer is it?
- Prognostic: Is it likely to develop a particular cancer?
- Predictive: Is this the optimal drug for particular cancer?
- Pharmacodynamics: What’s the optimal dose for one’s body?
- Reoccurrence: Will the cancer relapse?
These biomarkers are generally hormones, some proteins including glycoproteins, receptors, enzymes, changes in tumor (like tumor volume) and genetic mutations.
Some biomarkers reflected in leukemia, multiple myloma, brain, ovarian and testicular cancers are discussed below.
Leukemia: Leukemia is a group of cancers that usually begins in the bone marrow and results in abnormal white blood cells (WBCs). Leukemia is of two types – lymphocytic and myeloid leukemia (ML).
Recently, microRNAs from blood have become an attractive biomarker for early detection and even classification of lymphocytic leukemia.
More than 90% of ML cases are due to genetic abnormalities characterized by famous ‘Philadelphia chromosome’ and BCR-Abl (an abnormal genetic sequence of tyrosine kinase protein which exists in cancer cells only). Both these biomarkers can be detected by a simple blood test followed by chromosome analysis. Gleevec was the first drug specifically acting against BCR-Abl in chronic ML.
Diagnostic blood tests for multiple myeloma(a cancer of plasma cells) include, the beta-2 microglobulin (β2-M) level considered to be a measure of tumor burden and the C-reactive protein an indirect measurement of number of cancer cells. Myloma cells secrete certain proteins that can be identified by serum electrophoresis and urine Bencejones protein estimation.
Brain tumor: Currently, two biomarker tests are available for brain tumors – MGMT methylation and 1p/19q. The MGMT test is used to determine the levels of activity of the MGMT protein involved in DNA repair. MGMT biomarker testing is suitable for: anaplastic astrocytoma, anaplastic oligodendroglia, anaplastic oligoastrocytoma, glioblastoma, anaplastic gliomas. The 1p/19q test may predict brain tumors such as oligodendroglia, anaplastic oligodendroglia, oligoastrocytoma, anaplsticoligoastrocytoma as well as in making decisions about treatment selection.According to the recent study, detection of the biomarker netrin using a simple urine test helps to predict the relapse of brain tumor.
Ovarian cancers: The CA 125 test has been the gold standard for monitoring patients diagnosed with ovarian cancer but is limited in its sensitivity as well as ability to detect different types of ovarian cancer. CA 125 is usually measured from a blood sample but can be detected in fluid from chest or abdominal cavity. It is present in greater concentration in ovarian cells than in other cells. Another marker HE4 is elevated in epithelial ovarian cancers, the most common type. Using ROMA (a calculation combining results of CA 125 and the HE4) classifies women as being at low or high risk for ovarian cancer. This triage is FDA approved.
Testicular cancer: These cancers are usually diagnosed after a man feels a mass or sensations of ‘heaviness’ in his testis. Non-testicular germ cell tumours can be found in the abdomen or chest and can be secretory or non-secretory.
High levels of any one of the three biomarkers, alpha-fetoprotein (AFP), beta human chorionic gonadotropin (hCG), and lactate dehydrogenase (LDH), may indicate a germ cell tumor that develops in testis or elsewhere. High AFP levels can also help identify the type of germ cell tumor.During treatment, changes in their levels can tell your doctor whether the tumor is responding to treatment.