Annexin A3 in urine: a highly specific noninvasive marker for prostate cancer early detection.

PURPOSE

In prostate cancer cases the early diagnosis of tumors carrying a high risk of progression is of the utmost importance. There is an urgent clinical need to avoid unnecessary biopsies and subsequent overtreatment. We validated annexin A3 as a diagnostic marker for prostatic disease in typical clinical populations and relevant segments, such as patients with a negative digital rectal examination and low prostate specific antigen.

MATERIALS AND METHODS

We performed a blinded clinical study (ClinicalTrials.gov Identifier NCT00400894) from September 2005 to January 2007 in 591 patients who were continuously recruited from 4 European urological clinics. Urine was obtained directly after digital rectal examination and the annexin A3 concentration in urine was quantified by Western blot. Statistical analysis included combinations of annexin A3 with total, percent free, complexed and percent complexed prostate specific antigen.

RESULTS

Combined readouts of prostate specific antigen and urinary annexin A3 were superior to all others with an area under the ROC curve of 0.82 for a total prostate specific antigen range of 2 to 6 ng/ml, 0.83 for a total prostate specific antigen range of 4 to 10 ng/ml and 0.81 in all patients. The best performing prostate specific antigen derivative was percent free prostate specific antigen with an area under the ROC curve of 0.68 for a total prostate specific antigen range of 2 to 6 ng/ml, 0.72 for a total prostate specific antigen range of 4 to 10 ng/ml and 0.73 in all patients. Annexin A3 has an inverse relationship to cancer and, therefore, its specificity was much better than that of prostate specific antigen.

CONCLUSIONS

Annexin A3 quantification in urine provides a novel noninvasive biomarker with high specificity. Annexin A3 is complementary to prostate specific antigen or to any other cancer marker. It has a huge potential to avoid unnecessary biopsies with a particular strength in the clinically relevant large group of patients who have a negative digital rectal examination and prostate specific antigen in the lower range of values (2 to 10 ng/ml).