Screening for autoantibodies to tumor protein TP53 (also known as p53) could detect ovarian cancer earlier than cancer antigen 125 (CA125) testing, a recent study suggests.
“Ovarian cancer is detected in a late stage in more than three-fourths of patients,” said Robert Bast Jr., M.D., a professor in the Department of Experimental Therapeutics and vice president for the Office of Translational Research at The University of Texas MD Anderson Cancer Center. “Earlier detection could help cure 13%–30% of all patients with currently available surgery and chemotherapy.”
Dr. Bast added that screening with annual CA125 testing and ultrasonography for the early detection of ovarian cancer in women at normal risk for the disease is being evaluated through trials coordinated by MD Anderson in the United States and by University College London in the United Kingdom. However, other biomarkers are needed because CA125 is expressed by only 80% of ovarian cancers.
Because TP53 gene mutations and TP53 overexpression occur in virtually all high-grade serous ovarian cancers, Dr. Bast and his colleagues hypothesized that the immune response to TP53 could be used as an ovarian cancer biomarker that is detectable before CA125 levels rise as ovarian cancers grow and spread.
The researchers developed a novel immunoassay for measuring TP53-specific autoantibody titers in small volumes (2 μL) of serum. Using the assay, the researchers analyzed archived blood samples from the United Kingdom Collaborative Trial of Ovarian Cancer Screening.
Elevated anti-TP53 autoantibody titers were detected in about 25% of the samples from women who were later diagnosed with ovarian cancer. In ovarian cancer patients with elevated CA125 levels, anti-TP53 autoantibodies rose a mean of 13.5 months before CA125 levels began to increase. In ovarian cancer patients without elevated CA125 levels, elevated anti-TP53 autoantibodies were detected a mean of 33 months before the cancer was diagnosed.
The researchers concluded that screening for anti-TP53 autoantibodies, used in conjunction with CA125 screening, could aid in the early detection of ovarian cancer. “Among more than 100 biomarkers tested to date, this is the first that has been elevated prior to CA125 in women with ovarian cancer,” Dr. Bast said.
Dr. Bast and his colleagues reported their findings in April at the American Association for Cancer Research Annual Meeting.
OncoLog, June 2015, Volume 60, Issue 6