Cancer Treatment Centers of America

Annual blood tests may be the key to diagnosing ovarian cancer early

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There are currently no screening tests for ovarian cancer. As a result, it's uncommon for women to be diagnosed with the disease in its earliest stages—when it's most treatable. But a new study that analyzed women's blood samples every year offers hope for early diagnosis.

Researchers tracked levels of the protein CA-125, a known marker for ovarian cancer, in 4,051 post-menopausal women over 11 years. The researchers tracked changes in CA-125 levels and women with sudden increases in the protein were referred to a gynecologist and had an ultrasound.

Of the study participants, 117 were labeled as high-risk and recommended for a transvaginal ultrasound.

Ten of the women who had ultrasounds underwent surgery, according to the study published in the Aug. 26 issue of the journal Cancer. Of those 10 women:

  • Four had early-stage ovarian cancer
  • Three had benign cysts
  • Two had ovarian tumors that were unlikely to become malignant
  • One had endometrial cancer

The study found that annual testing for CA-125 resulted in a false positive in only 0.1 percent of patients. That means one woman in 1,000 would be diagnosed with ovarian cancer after annual testing when she did not have it. The women with invasive ovarian cancers were treated and reported to be cleared of the disease between four and 42 months after treatment. Screening during the study did not detect ovarian tumors in two women in but, the researchers said, both had tumors of low malignant potential.

Early diagnosis improves survival rates

Only about 30 percent of ovarian cancers are diagnosed early. If caught early, 75 to 90 percent of patients survive at least five years, according to the researchers. The long-term survival rate for advanced stage ovarian cancer is less than 30 percent.

"One of the reasons ovarian cancer is so deadly is that most patients present with advanced stage disease, where the cancer already has spread to multiple other sites beyond the ovary," said Justin Chura, MD, Medical Director of Gynecologic Oncology at CTCA in Philadelphia. "This is why we often recommend ultra-radical surgery to remove all cancer in the abdominal-pelvic cavity and then we treat with chemotherapy."

So far, screening for CA-125 has not been shown to be a useful test for ovarian cancer because common conditions also can cause high levels of the protein. These conditions include:

  • Uterine fibroids
  • Endometriosis
  • Pelvic inflammatory disease
  • Cirrhosis
  • Pregnancy
  • Normal menstruation

In addition, some women with ovarian cancer do not have high CA-125 levels and many women with early-stage ovarian cancer have normal CA-125 levels. No major medical organization endorses routine blood tests to detect the protein.

The CA-125 study shows promise for detecting ovarian cancer at an early stage, Dr. Chura said. While the results are encouraging, he stressed that it would be premature to start offering routine CA-125 screening as part of preventive health care.

"For a screening test to truly be effective, we need to demonstrate that the test leads to fewer women dying of ovarian cancer compared with women who do not undergo screening," Dr. Chura said. "Nonetheless, this study puts us further down to path toward detecting ovarian cancer at an early stage, when chances for cure are much higher."

A larger, randomized study currently underway in the United Kingdom uses the same screening protocol and could offer additional insight. The study follows more than 200,000 women, with results expected by 2014.

Learn more about the symptoms and risk factors of ovarian cancer.