New Blood Test Improves Prostate Cancer Diagnosis

The IsoPSA assay, a blood test for prostate cancer, improved diagnostic accuracy of disease presence and grade of disease compared with concentration-based assays, according to the findings of a preliminary study.

“IsoPSA is a structure-based (rather than concentration-based) assay that agnostically interrogates the entire spectrum of structural changes of complex [prostate-specific antigen],” the researcher wrote.
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The multicenter prospective study included 261 men scheduled for prostate biopsy between August 2015 and December 2016 at 5 academic and community center clinics. The performance of IsoPSA at detecting the presence of prostate cancer verses no cancer, and detecting the presence of high-grade disease verses the presence of low-grade or benign disease were assessed as the main outcomes. 

Overall, 139 patients out of 261 (53.3%) had prostate cancer, and 88 (33.7%) had high-grade prostate cancer.

The area under the receiver operating characteristic curve was 0.79 for any cancer verses no cancer, and 0.81 for high-grade verses low-grade or benign disease presence. In addition, decision curve analysis showed a superior net benefit of IsoPSA over no biopsy, all biopsy, and the Modified Prostate Cancer Prevention Trial Risk Calculator 2.0.

False-positive biopsies were reduced by 48% and the rate of false-positives for identifying men with high-grade verses men with low-grade or benign disease risk was reduced by 45%.

“The results show that if adopted clinically, IsoPSA could significantly reduce the rate of unnecessary biopsies by almost 50% while preserving both [positive predictive value] and [negative predictive value] for detection of cancer versus no cancer and of high-grade [prostate cancer] versus low-grade [prostate cancer]/benign histology,” the researchers wrote.

“In conclusion, this study demonstrates for the first time that use of a structure-based rather than concentration-based assay of PSA has better diagnostic accuracy for detecting any cancer and high-grade cancer in a cohort of men undergoing biopsy for standard clinical indications,” the researchers concluded. “Once validated, use of IsoPSA may substantially reduce the need for biopsy, and may thus lower the likelihood of overdetection and overtreatment of nonlethal [prostate cancer].”

—Melissa Weiss

Reference:

Klein EA, Chait A, Hafron JM, et al. The single-parameter, structure-based IsoPSA assay demonstrates improved diagnostic accuracy for detection of any prostate cancer and high-grade prostate cancer compared to concentration-based assay of total prostate-specific antigen: a preliminary report [published online March 17, 2017]. Eur Urol.  http://dx.doi.org/10.1016/j.eururo.2017.03.025.