Ovarian Cancer Diagnosis

Several diagnostic approaches can be followed when ovarian cancer is suspected. The CA125 blood test, which measures a blood protein that is usually elevated in a woman who has ovarian cancer, should not be used as a screening or diagnostic tool. Rather, it is a tool for monitoring disease recurrence in patients.  Women also should know that Pap smears detect cervical cancer, not ovarian cancer.

A transvaginal ultrasound, computed tomography scan or a magnetic resonance imaging will allow the doctor to visualize the ovaries to see if a tumor is present. The final step is a biopsy, which removes a sample of ovarian tissue by laparoscopy and examines it under the microscope. Biopsy is the only way to diagnose ovarian cancer with certainty, but cancer cells may be detected in fluid obtained from the abdomen in women with ascites.

Ultrasound uses high-frequency sound waves to construct an image of deep body tissues that is displayed on a video screen and photographed for analysis.

Computed tomography uses a rotating X-ray beam directed at the body from various angles; a computer processes information from the scan to produce a detailed image of a selected area of the body. Magnetic resonance imaging uses a magnetic field and radio frequency waves rather than X-rays to create images of specific areas of the body.  -Used with permission from HopkinsHealth, copyright Johns Hopkins.

Blood Test Research 

The current limitations of CA125 testing for ovarian cancer have generated a need for better serum tests for early detection and monitoring for recurrence of disease. It is still not yet clear whether a single serum biomarker, a panel of biomarkers, or a combination of biomarkers and imaging studies will provide the most accurate approach to detecting sub-clinical ovarian cancer.

A great deal of attention and resources has been directed toward a field of study referred to as proteomics based on results of a study reported in 2002 in the medical journal Lancet. In that study, Petrocoin et al reported that a blood test based on pattern-recognition proteomics analysis of serum showed a sensitivity of 100%, specificity of 95%, and positive predictive value of 94% in identifying early ovarian cancer. The consumer magazine Health named the test one of the top ten medical advances of the year.

Soon after publication of these experimental results, commercial rights to develop the test were licensed from the U.S. government to a company called Correlogic Systems. In November 2002, Correlogic granted licenses to two larger firms, Quest Diagnositics and the Laboratory Corporation of America, to market the test under the brand name OvaCheck.

Proteomics relies on gravity and electric fields to separate serum proteins. Each protein is then given a number, called the m/z value, which represents the ratio of its charge to mass. Bioinformatics technology is then used to cull the enormous datastreams generated by mass spectrometry analysis of serum proteins contained within a patient (or patients) blood samples to identify a discriminating series or pattern of proteins or protein fragments based on their m/z values that, when examined on the whole, can separate affected (ovarian cancer) from unaffected patients (no disease).

Recently, several independent groups have raised questions about the reliability and reproducibility of OvaCheck. One criticism has been that most of the discriminating proteins in the study had m/z values less than 500, which many experts consider questionable due to an increased possibility of experimental artifact and measurement error. Another criticism of the study has been that ability of novel serum protein patterns to discriminate ovarian cancer patients from unaffected individuals has not been able to be reproduced by other investigators (See reference below on Check E.).

On February 7, 2004, the Society of Gynecologic Oncologist issued a position statement on OvaCheck, after a comprehensive review of the literature: More research is needed to validate the tests effectiveness before offering it to the general public (www.sgo.org/policy/position_Statement.cfm). Currently, additional research is ongoing in an attempt to validate the utility of proteomic technology for the early detection of ovarian cancer.  Read more on Johns Hopkins proteomic blood tests for ovarian cancer.

References

Petricoin EF, Ardekani AM, Hitt BA et al. Use of proteomic patterns in serum to identify ovarian cancer. Lancet 2002; 359: 572. [Abstract]

Check E. Proteomics and cancer: running before we can walk? Nature. 2004 Jun 3;429(6991):496-7. [No abstract available]