Is race a factor in exercise and prostate cancer prevention?


We have known for some time that regular exercise may lower risk for prostate cancer. Indeed, a study by Clarke and Whittemore published in 2000 suggested that men who take little to no exercise may be 1.7 times more likely to be diagnosed with prostate cancer than those who exercise with a degree of regularity.

In 2009, a study by Moore et al. that involved data from 160,006 white men and 3,671 black men, all aged between 51 and 72 years, suggested that “Regular physical activity may reduce prostate cancer risk among black men, with activity during young adulthood possibly yielding the greatest benefit.” However, the same study found no association whatsoever between risk for prostate cancer and exercise among white males. Now a new study by Singh et al. (“Exercise linked with reduced prostate cancer risk in Caucasians but not African Americans”), published on line today in Cancer, has shown exactly the opposite!  (Note that the abstract of this article is not yet available on line, as of this morning, but The “New” Prostate Cancer InfoLink has been able to review the entire text of this article.)

It has to be recognized immediately that this new study by Singh et al. is relatively small. On the other hand, it was a carefully constructed, prospective study.

Singh et al. used a self-reported survey to collect data on exercise from 540 men with no diagnosis of prostate cancer who were scheduled for prostate biopsy at the Veterans Affairs Medical Center in Durham, North Carolina. The exercise data were used to estimate exercise behavior in terms of metabolic equivalent or MET, measured in hours per week.

Here are the study findings:

  • 233/540 men were excluded from the study for a variety of reasons (largely related to failure to complete the survey or document other relevant data like the height or weight of the patient).
  • Of the remaining 307 men
    • 143 (47 percent) were of black ethnicity
    • 164 (53 percent) were white
  • 125/307 men were diagnosed with prostate cancer on biopsy.
    • 64/143 black men (45 percent) were positive on biopsy
    • 61/164 white men (37 percent) were positive on biopsy
  • 54/307 men were diagnosed with a Gleason score ≥ 7
    • 25/143 black men (17 percent) had a Gleason score ≥ 7
    • 29/164 white men (18 percent) had a Gleason score ≥ 7
  • There was no significant differencein quantity of exercise between the two ethnic groups
  • There was no significant association between exercise level and: age, PSA level, body mass index (BMI), family history, or prior biopsy status.
  • A higher level of MET hours  per week was associated with a decreased risk of positive biopsy among the white men (odds ratio [OR] = 0.89).
  • There was no association between exercise level and occurrence of positive biopsies among the black men.
  • Among all the men with cancer, there was an inverse relationship between exercise and risk for high-risk prostate cancer (OR = 0.87; P = 0.01).
    • This inverse relationship  was also significant among white males (OR = 0.82; P = 0.01).
    • It was not significant among black males (OR = 0.91; P = 0.25).

So what are we to make of this distinction between the results of this study by Singh et al. when compared to the results reported previously by Moore et al.? Alas, The “New” Prostate Cancer InfoLink is unable to answer that question.

6 Responses

  1. Does regular exercise help to control the progression of prostate cancer in Caucasians?

    Al Hagan Okotoks, Alberta, Canada

  2. The more interesting exercise studies, in my opinion, are those relating exercise to survivorship rather than exercise’s prophylactic impact.
    Recent studies by Kenfield, Chan et al. (Harvard and UCSF) suggest that exercise improves survivorship significantly. Also Chan’s small sample study suggesting that exercise produces tumor-fighting BRCA3 genes is seminal.

  3. Al:

    It certainly appears to.

  4. Rick:

    What do you mean when you write that “… exercise produces tumor-fighting BRCA3 genes is seminal”?

    Thanks,

    Al Hagan

  5. Hello Al:

    Take a look at this URL for an explanation. By seminal, I mean that if we can produce our own tumor-fighting genes by exercising daily, this should significantly impact all treatment protocols.

    You can also check http://www.medafit.org in the “Research” tab, under Prostate Cancer, for more links to studies.

    Feel free to be in touch if you have further questions.

    rd

  6. Rick:

    Thanks. Now I understand. I was diagnosed with prostate cancer on January 11, 2011; PSA 8.6. Have had total of three biopsies to date; Gleason 3 + 3. Since restarting an active exercise program (daily, which in part includes a 4-mile indoor track walk/run/sprint, stretching, light use of weights, etc.) my PSA is now 4.9. This exercise is also tied to more rigorous attention to diet. Still on active surveillance and seen by my urologist every 6 months + PSA test. I am 71 and have more energy than when I did not exercise for several years (used to do lots of marathons, half-marathons, and 5 and 10 k runs). And, perhaps more importantly, I am able to carry out my duties as my wife’s primary care giver. (She is in 5th and final stage renal failure, undergoing daily dialysis and hoping for a kidney donor).

    Al Hagan

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