New blood marker may predict prostate cancer spread to lymph nodes

A new blood test that measures levels of endoglin appears to accurately predict 98% of prostate cancers that will spread to regional lymph nodes, according to a study published in Clinical Cancer Research (2008; 14:1418-22). Endoglin is a plasma biomarker that has been previously shown to predict the spread of colon and breast cancer.

“For prostate cancer, we have hit the limit of our ability to classify risk in these patients before initial surgery,” said study co-author Shahrokh F. Shariat, MD, of the University of Texas Southwestern Medical Center, Dallas. “We currently use PSA, Gleason grade, and a rectal exam, but the predictive value of those three tests is inadequate for predicting what cancers will spread.”

“Although it is recognized that pelvic lymphadenectomy can provide important staging and prognostic information, it is still not clear in whom this procedure should be done,” added co-author Claus G. Roehrborn, MD, also of UT Southwestern. “Doing pelvic lymphadenectomy on all patients is not universally practiced, as this procedure could be time consuming and is not without morbidity. As such, it would be of tremendous benefit to have an accurate blood marker that identifies patients in whom pelvic lymphadenectomy should be done.”

In the study, researchers observed 425 patients who had undergone surgery to remove both their prostates and associated pelvic lymph nodes. They measured the levels of plasma endoglin using a commercially available blood test. Higher plasma endoglin levels were associated with an increased risk of cancer spread to the lymph nodes. Each 1 ng/mL increase of plasma endoglin increased the risk for cancer spread into the lymph nodes by 17%.

When researchers added endoglin levels to their usual methods of prediction, the accuracy improved from 89.4% without endoglin to 97.8%. Blood levels of endoglin may allow physicians to predict the risk of cancer spread at an earlier stage and with higher accuracy than currently available methods, according to the researchers.