PCa biomarkers: Hope for at-risk men

"What we need most are markers that selectively identify significant cancers, in order to reduce unnecessary biopsies and over-diagnosis," writes Stacy Loeb, MD, MSc.

Stacy Loeb, MD, MSc

Dr. Loeb,

African-American men are at a substantially greater risk of prostate cancer, with an incidence of 208.7 per 100,000 compared to 123.0 per 100,000 U.S. Caucasian men (CA Cancer J Clin, epub ahead of print, Feb. 22, 2016). Meanwhile, African-American men also have a significantly higher risk of prostate cancer death, with a rate of 47.2 per 100,000 compared to 19.9 per 100,000 U.S. Caucasian men. These figures highlight the importance of optimizing early prostate cancer detection in the African-American population.

Several new biomarkers are commercially available to aid in prostate biopsy decisions. These include blood tests such as the 4Kscore and Prostate Health Index (phi), which studies consistently show to be more specific than total PSA for clinically significant prostate cancer (Eur Urol 2015; 68:464-70; J Urol 2015; 193:1163-9). Both the 4Kscore and phi are included in the 2015 National Comprehensive Cancer Network guidelines as optional secondary tests for initial or repeat prostate biopsy decisions. The PCA3 urine test is another commercially available marker that can be used to aid in repeat prostate biopsy decisions.

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Comparative studies from Europe have shown that the 4Kscore and phi perform similarly to predict biopsy outcome (Eur Urol 2015; 68:139-46), and that phi outperforms PCA3 for the identification of clinically significant disease (Prostate 2015; 75:103-11). In fact, one of the key drawbacks of using PCA3 in clinical practice is the conflicting data on its relationship with aggressive disease. What we need most are markers that selectively identify significant cancers, in order to reduce unnecessary biopsies and over-diagnosis.

Next: "Less is known about the comparative performance of these new markers in the African-American population."

Less is known about the comparative performance of these new markers in the African-American population. A recent study confirmed that phi predicts aggressive pathology in African-American men (Urology, epub ahead of print, Dec. 10, 2015). Meanwhile, new data presented at the 2016 Genitourinary Cancers Symposium by Feibus et al suggest that PCA3 added to the prediction of high-grade disease in African-American men, but not in Caucasian men (see article). These findings may help to explain the mixed performance of PCA3 in previous studies and highlight the importance of evaluating new markers in ethnically heterogeneous populations.

Hopefully, the availability of new markers with improved performance in this population can help to enhance the diagnostic paradigm for African-American men in the future.