Tumor markers
Tumor markers are chemicals produced by the cancerous cells that are detected in the blood of the patients, but they are also produced by some normal cells of the body. Their level in blood is significantly elevated in cancerous conditions as well as in some noncancerous conditions. That is why they only serve the screening purpose; they alone can’t confirm the diagnosis of cancer. Additional investigations are done along with it to confirm the diagnosis, but they always serve as an important tool towards diagnosis of cancer.
Examples
Following are the examples of tumor markers and associated cancerous conditions where their blood levels are elevated.
Sr. no. Name of the tumor marker Associated cancerous condition
1 Prostate specific antigen (PSA) Prostate cancer
2 Cancer antigen-125 (CA-125) Ovarian cancer
3 Calcitonin Medullary thyroid cancer
4 Alfa-fetoprotein (AFP) Liver cancer
5 Human chorionic gonadotropin (HCG) Germ cell tumors like testicular and ovarian cancers
Individual tumor markers
Prostate specific antigen (PSA)
PSA is normally produced by prostate gland. Most men have PSA level under 4 ng/mL. This value is used as a cut-off point. Elevated PSA level in blood may indicate prostate cancer and noncancerous conditions like inflammation of prostate and enlarged prostate. Men with prostate cancer often have PSA levels higher than four, although cancer is a possibility at any PSA level. Additional clinical examinations and laboratory investigations are done to confirm the diagnosis of prostate cancer.
Cancer antigen-125 (CA-125)
CA-125 is a protein produced mainly by ovarian cancer cells and also by some other cancerous cells. It is also produced in small amounts by normal cells. CA-125 test is usually used to assess the response to the treatment of ovarian cancer and its relapse. Normal value of CA-125 is 35 units per mL. It is alone not used to screen ovarian cancer as elevated levels may be due to false positive results. Additional tests are required to confirm the diagnosis of ovarian cancer.
Calcitonin
Calcitonin is produced by one of the cells of thyroid gland. It is used as a screening test for medullary thyroid cancer where level of calcitonin is elevated. Additional investigations are done to confirm the diagnosis. Elevated level after surgery suggests recurrence of the disease.
Alfa fetoprotein (AFP)
AFP is a plasma protein produced by the yolk sac and liver during development of fetus in the womb of the pregnant mother. Measurement of blood level of AFP has got various clinical significances. One of them is detection of liver cancer, spreading liver cancer and germ cell tumor where is used as a biomarker for cancer detection.
Human chorionic gonadotropin (HCG)
HCG is produced by the placenta of the pregnant mother. Like AFP, measurement of HCG has got various clinical significances. Blood level of HCG is elevated in certain cancerous conditions where cancerous cells produce HCG. Elevated levels suggest germ cells tumors like testicular and ovarian cancers. Elevated level in male suggests testicular cancer. In non-pregnant female in combination with AFP, HCG serves as a reliable tumor marker for ovarian cancer.
These are some important tumor markers discussed in the text. There are other chemicals that serve as tumor markers also. They mostly serve screening purposes as well as monitoring purposes to detect relapse or recurrence of cancer.
