Natural killer cell activity and prostate cancer risk in veteran men undergoing prostate biopsy

Background: A previous pilot study found that men with a positive prostate biopsy had low numbers of circulating natural killer (NK) cells, compared to biopsy negative men. Methods: To confirm these data, we analyzed differences in NK cells from 94 men undergoing prostate biopsy to determine whether NK cells could predict for a positive biopsy. NK cells activity (NKA) was measured by an in vitro diagnostic system, with a pre-defined cut-off value for NKA at 200 pg/mL. Logistic regression and receiver operator characteristics (Area Under the Curve (AUC)) analyses were used to test the diagnostic value of NKA. Results: The NKA test performance showed specificity of 88%, positive predictive value of 84%, sensitivity of 34%, and a negative predictive value of 41%. Among the 94 men analyzed, NKA was not significantly linked with age, race, digital rectal examination (DRE), prostate volume, PSA or biopsy grade group (all P ≥ 0.14). In multivariable logistic regression analysis, the odds ratio (OR) of low NKA (<200 pg/mL) for the detection of PC was 4.89, 95%CI 1.34–17.8, with a ROC area under the curve of 0.79 in all participants and increasing to 0.83 and 0.85 for the detection of PC and high-grade PC, respectively, among men with a normal DRE. Conclusions: Men with a low NKA value had five-times higher odds of PC at biopsy. The implementation of this NKA assay in the clinic together with PSA may help to advise patients with the highest risk of PC whether, or not, to undergo a prostate biopsy.