Download CA-125 tumor marker

Running Head: CA-125
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CA-125 Tumor Marker
For
Ovarian Cancer
Tanya Staton
Concordia University
08/20/13
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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.
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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 concern and 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 a Papanicolaou Test (PAP smear) can detect ovarian cancer. A
PAP smear can only detect cervical cancer (cdc.gov).
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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, colon and rectal carcinomas 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.
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http://franklin.liquidweb.com/~gynoncol/wp-content/uploads/2010/10/Graph.gif
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 not overly 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 successfully administer 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.
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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 be reliable 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).
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Reference:
Gynecological Onocology. (2010). CA 125. Retrieved from: http://www.gynoncology.com/ca-125/
Center for Disease Control and Prevention. (2012). Ovarian Cancer. Retrieved from:
http://www.cdc.gov/cancer/ovarian/pdf/ovarian_facts.pdf
Bast, R. (2003). Status of Tumor Markers in Ovarian Cancer Screening. Retrieved from:
http://www.ncbi.nlm.nih.gov/pubmed/12743135
Gallenburg, Mary. (2011).Ovarian Cancer. Retrieved from:
http://www.mayoclinic.com/health/ca-125/HQ00366
MD Anderson. (2010) CA-125 Change Over Time Shows Promise as Screening Tool for Early
Detection of Ovarian Cancer. Retrieved From
http://www.mdanderson.org/newsroom/news-releases/2010/ca-125-change-over- timeshows- promise-as-screening-tool-for-early-detection-of-ovarian-cancer.html
National Cancer Institute. (2013). Ovarian Cancer Screening. Retrieved from:
http://www.cancer.gov/cancertopics/pdq/screening/ovarian/HealthProfessional/page2
Stoppler, M. (2009). CA 125. Retrieved from
http://www.medicinenet.com/ca_125/page2.htm#tocg
Fris, R. and Sellers, T. (2009) Epidemiology For Public Health Practice. Sudbury, MA: Jones &
Bartlett