Men with a low number of circulating natural killer (NK) cells are at higher risk of having prostate cancer (PCa) diagnosed at biopsy, according to new data that confirms the findings a previous pilot study.

Adriana C. Vidal, MD, of the Samuel Oschin Comprehensive Cancer Center at Cedars-Sinai Medical Center in Los Angeles, and collaborators analyzed differences in NK cells from 94 men undergoing prostate biopsy to ascertain whether NK cell values could predict a positive biopsy. Investigators used an in vitro diagnostic assay to measure NK cell activity (NKA), with a predefined cut-off value for NKA of 200 pg/mL.

The NKA test performance demonstrated a specificity of 88%, positive predictive value of 84%, sensitivity of 34%, and negative predictive value of 41%, Dr Vidal’s team reported in Cancer Epidemiology. NKA was not significantly associated with age, race, digital rectal examination, prostate volume, PSA, or biopsy grade group, according to the investigators.

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On multivariable analysis, an NKA value less than 200 pg/mL was associated with nearly 5-fold increased odds of having a positive biopsy compared with a higher NKA value.

Implementation of this NKA assay in the clinic, together with PSA values, may help to advise patients with the highest risk of PCa whether or not to undergo a prostate biopsy, the authors concluded.

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The current investigation confirms the findings of a pilot study showing that NKA values below 200 pg/mL were more likely than those with higher values to have PCa at prostate biopsy (86% vs 31%).

NK cells are cytotoxic lymphocytes of the innate immune system, Dr Vital and her collaborators explained. They play a key role in anti-tumor immunity and immunosurveillance, including production of cytokines and chemokines that mediate anti-tumor responses, they noted. Previous studies have found an association between NK cells and different stages of PCa.


Vidal AC, Howard LE, Wigins E, et al. Natural killer cell activity and prostate cancer risk veteran men undergoing prostate biopsy. Cancer Epidemiol. 2019;62:101578. doi: 10.1016/j.canep.2019.101578