Does prostatic inflammation increase risk for prostate cancer?


A new paper just published in Cancer, and based on information from patients gathered during the REDUCE study has suggested that men who have acute and/or chronic inflammation of the prostate on biopsy are actually at reduced risk for prostate cancer.

This new study by Moreira et al. was, however, initiated to see if it would support exactly the opposite hypothesis, i.e., that men who had a first biopsy that was negative for prostate cancer but positive for signs of inflamed prostatic tissue were at increased risk for a finding of prostate cancer on a second biopsy.

The authors used data from the REDUCE trial because all participants in this trial were scheduled to undergo at least two biopsies: one at baseline to make sure that patients did not have cancer at time of study entry, and another later on to see if treatment with dutasteride had reduced their risk for prostate cancer. The authors were able to use the biopsy samples and related data from this trial to assess risk associated with the presence of inflamed prostatic tissue.

Here is what they report:

  • The study involved 6,238 men between 50 and 75 years of age who had
  • At baseline, all the men enrolled in the trial
    • Had a PSA level between 2.5 and 10 ng/ml
    • Had a biopsy that was negative for prostate cancer
  • All participants received a follow-up biopsy at 2 years and some participants received another follow-up biopsy at 4 years.
  • All prostate biopsy data and specimens were centrally reviewed for risk of prostate cancer, acute inflammation, and chronic inflammation.
  • The presence of acute and/or chronic inflammation on the baseline biopsy was assessed against the presence of previously undiagnosed prostate cancer on follow-up biopsies on patients at 2 and 4 years.
  • At baseline
    • 46/6,238 men (< 1 percent) had a biopsy result that was positive for acute inflammation alone.
    • 3,931/6,238 men (63 percent) had a biopsy result that was positive for chronic inflammation alone.
    • 892/6,238 men (14 percent) had a biopsy result that was positive for both acute and chronic inflammation.
  • At the time of the second (2-year) biopsy, 900 men (14 percent) were newly diagnosed with prostate cancer.
  • Among these 900 newly diagnosed patients, compared to men with no inflammation found at the baseline biopsy
    • For the men who had acute inflammation at the baseline biopsy
      • Univariate risk for prostate cancer was significantly reduced (odds ratio [OR] = 0.65)
      • Multivariate risk for prostate ccner was signifciantly reduced (OR = 0.75)
    • For the men who had chronic inflammation at the baseline biopsy
      • Univariate risk for prostate cancer was significantly reduced (OR = 0.61)
      • Multivariate risk for prostate ccner was signifciantly reduced (OR = 0.65)
  • At the time of the third (4-year) biopsy, only acute inflammation at baseline was associate with reduced risk for a diagnosis of prostate cancer.

Now it would be a mistake to over-interpret these data, but it does appear that prostate inflammation is not associated with any increase in risk for prostate cancer, and that, furthermore, the presence of inflamed prostatic tissue on an initial biopsy is actually associated with a significantly reduced risk for a later finding of prostate cancer (at least in the relatively short term).

2 Responses

  1. Am I missing something here? This study tells me things that are already well established:

    (1) PSA is a non-specific test, detecting both prostatic inflammation (prostatitis) and prostate cancer, among other things
    (2) Some men detected with elevated PSA (2.5-10) will be found on biopsy to have prostate cancer; some will have prostatitis; some will have both; some will have neither.

    (3) A first systematic TRUS-guided biopsy sometimes misses the cancer. The probability of detecting it increases with the number of biopsies. The probability of developing prostate cancer goes up with age.

    It is also possible that the inflammation interferes with the biopsy detection of the cancer through some other mechanism (e.g., swollen tissue decreases the probability that a random biopsy will find the cancer, inflammation confounds Gleason pattern determination, etc.)

    It seems that your title question “Does prostatic inflammation increase [or decrease] risk of prostate cancer?” cannot be answered by this study. It can only show association, not causation. It seems to me that the above three well-known points explain the association seen here.

  2. Dear Allen:

    The precise phrasing of the heading was very deliberate. There has long been a perception by a subset of the prostate cancer research community that prostate inflammation would be shown to be associated with an increased risk for later diagnosis of prostate cancer. This is known to be the case in some other forms of cancer.

    This study does not resolve this issue in its entirety, but what it does do is provide strong suggestive evidence that a finding of prostate inflammation on a first biopsy is not associated with an increased risk for subsequent diagnosis of prostate cancer. As you point out, this is an association, not a cause and effect, but it would tend to eliminate the idea that a man with prostatic inflammation on a first biopsy needs to be re-biopsied solely on the basis of having an inflamed prostate. He still might need to be rebiopsied for other reasons, however (e.g., if his PSA continues to rise).

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