CA-1251
CA-125 Tumor Marker
For
Ovarian Cancer
Tanya Staton
Concordia University
08/20/13
Abstract
Ovarian cancer is the number one cause of death caused from gynecological cancers. Any woman can be diagnosed with ovarian cancer, but most cases occur in women age 40 or above. Carcinogenic Antigen 125 (CA-125) is a tumor marker that can aid in the diagnosis and monitoring of ovarian carcinoma. There is debate to continue this screening procedure because the CA-125 tumor marker is not a very specific or sensitive test in diagnosing ovarian cancer. The tumor marker can however be beneficial in monitoring the status of a patient.
The Center for Disease Control and Prevention estimates that 20,000 women a year will be diagnosed with ovarian cancer and a majority of the women diagnosed will have already progressed to more advanced stages (cdc.gov).According to the CDC, ovarian cancer causes more deaths than any other cancer of the female reproductive system and is also the eighth most common cancer among women (cdc.gov).Ovarian cancer is a carcinoma that starts in the ovaries. The malignant tumor may originate in germ cells, stromal tissue or epithelial tissue of the ovaries. Ovarian cancer of the epithelial tissue is the most common and deadliest form of the carcinoma (cancer.gov). Although ovarian cancer causes the most deaths in gynecological cancers,doctors can easily treat it if they detect it in the early stages.
Any woman—regardless of age—can develop ovarian cancer, but 90 percent of cases are seen in women over the age of forty (cdc.gov). Family history of ovarian cancer, previous cancer or gynecological problems like endometriosis can increase a woman’s chance of getting ovarian cancer. Difficulty getting pregnant or never giving birth can also potentially increase the odds.However, a majority of women can develop ovarian cancer without being exposed to any risk factors (cdc.gov). Signs of ovarian cancer include back pain, feeling bloated and change in urinary habits, but the main symptom of ovarian cancer is vaginal bleeding or abnormal discharge. Vaginal bleeding in post-menopausal women is the main concernand is a huge indicator that ovarian cancer could be a possibility (cdc.gov). Other symptoms can be present, but experts advise women to listen to their bodies and see a physician if something changes.It is a common misconception that aPapanicolaouTest(PAP smear) can detect ovarian cancer. A PAP smear can only detect cervical cancer (cdc.gov).
If a physician suspects ovarian cancer, they can perform a rectovaginal pelvic exam or a transvaginal ultrasound. A Cancer Antigen 125 (CA-125) blood test is available to help aid in the diagnosis and track the progression or regression of the disease (cdc.gov). CA-125 is a glycoprotein that is recognized by the antibody OC-125 in a female’s blood stream. Ninety percent of women will produce the CA-125 protein in advanced stages of ovarian cancer. A female with a normal CA-125 blood level will have a result that reads under 35 µ/mL (gynonology.com). A female with ovarian cancer should have an elevated CA-125.
CA-125 should not be the only diagnostic test done when determining if a patient has ovarian cancer. Other carcinomas like pancreatic, colonand rectalcarcinomas can also present with an elevated CA-125 level (gyonocology.com). Non-malignances like salpingitis (inflammation of the uterine tubes), pregnancy and renal failure can also cause a false positive CA-125 result (gyonocolgy.com). The CA-125 blood test is not a very sensitive test, because so many other disorders can cause an elevated CA-125 level. Sensitivity refers to the ability to correctly identify all screened individuals who actually have the disease (Friss & Sellers, 2009). The CA-125 blood test is not a very specific test as well. Specificity refers to a tests ability to identify non-diseased individuals who actually do not have the disease (Friis & Sellers, 2009). The CA-125 screening method also has a low positive predictive value (cdc.gov). A positive predictive value relates to the proportion of diseased individuals who actually have the disease being studied (Friis & Sellers). Therefore positive predictive value is directly proportional to sensitivity. Below is a figure which illustrates how a high positive predictive value test reflects the underlying condition.
Many studies have confirmed that CA-125 screening does not help in diagnosing ovarian carcinoma. One study included 78,216 women over the age of 55 who received a CA-125 blood test (Gallenburg, 2011). Results of the study showed that the tests did not reduce ovarian cancer deaths and actually proved that complications due to anxiety occurred because of false positives (Gallenburg, 2011). Another research study concluded that some women who have ovarian cancer never even had an elevated CA-125 level. Estimates show that only three percent of females with an increased CA-125 level actually have ovarian cancer because there are so many disorders that are associated with increased levels of the tumor marker (Stoppler, 2009). This once again proves that the blood test is notoverly beneficial in screening for ovarian cancer.
Although CA-125 is not specific or sensitive when diagnosing ovarian cancer, it can help in monitoring ovarian cancer (nlm.nih.gov). When physicians successfullyadminister treatment, the CA-125 levels will decrease and can achieve a specificity of 99.6 percent (nlm.nih.gov). The blood test sensitivity is still restricted and CA-125 may only detect 80 percent of early-stage cancers (nlm.nih.gov). A CA-125 blood test is also beneficial in monitoring recurrent cases of ovarian cancer (cdc.gov). An elevated CA-125 level is usually an indicator that the cancer is no longer in remission.
The CDC is currently conducting research studies to help increase knowledge about ovarian cancer. One study involved asking physicians if a CA-125 blood test actually aided in the diagnosis of ovarian cancer. The study showed 53 percent of physicians confirm that CA-125 blood tests help in diagnosis while 57 percent of oncologists said that it was not an effective screening method for asymptomatic women (cdc.gov). Another research study that is currently being conducted is a retrospective cohort study on ovarian cancer treatment patterns and outcomes (cdc.gov). This study examines staging, therapy, surgery and survival among women who were diagnosed between 1998 and 2000 (cdc.gov).
Many physicians that are knowledgeable about blood tests will not order a CA-125 blood level unless they are specifically prompted for it. The test is costly and most insurance companies will not pay for it because of the low specificity and sensitivity. There is no way to increase participation for women in choosing to be screened for ovarian cancer because in reality there really is not a particular test that can bereliable enough to screen for the carcinoma. Public health professionals and women need to advocate towards further research for a better screening process or diagnostic test. Dr. Lu, a physician at the University of Texas, sums up the screening method for ovarian cancer best when she says "finding a screening mechanism would be the Holy Grail in the fight against ovarian cancer because, when caught early, it is not just treatable, but curable” (mdanderson.org).
Reference:
Gynecological Onocology. (2010). CA 125. Retrieved from:
Center for Disease Control and Prevention. (2012). Ovarian Cancer. Retrieved from:
Bast, R. (2003). Status of Tumor Markers in Ovarian Cancer Screening. Retrieved from:
Gallenburg, Mary. (2011).Ovarian Cancer. Retrieved from:
MD Anderson. (2010) CA-125 Change Over Time Shows Promise as Screening Tool for Early Detection of Ovarian Cancer. Retrieved From time- shows- promise-as-screening-tool-for-early-detection-of-ovarian-cancer.html
National Cancer Institute. (2013). Ovarian Cancer Screening. Retrieved from:
Stoppler, M. (2009). CA 125. Retrieved from
Fris, R. and Sellers, T. (2009) Epidemiology For Public Health Practice. Sudbury, MA: Jones & Bartlett