Genetic ethnic ancestry and risk for prostate cancer diagnosis


It is becoming increasingly evident that there is a strong association between ethnic ancestry and risk for prostate cancer — at least among members of the US population. A new paper by Nyame et al., to be presented at the upcoming Genitourinary Cancers Symposium, has added to our knowledge in this area (see abstract no. 86; “Genetic ancestry and odds of prostate cancer diagnosis in African American and European American men”).

Specifically, Nyame et al. looked into the degree to which West African and Native American genetic ancestry affected risk for prostate cancer diagnosis among men who self-classified as European American and African American. To do this, they enrolled patients aged between 40 and 79 years of age who were undergoing prostate biopsies or routine prostate cancer screenings at outpatient clinics in Chicago, IL. Blood was drawn from all enrolled patients and used to genotype the patients for 105 “ancestry informative” genetic markers.

Here are the core study findings:

  • 857 men were enrolled, among whom
    • 296/857 (34.5 percent) were biopsied and diagnosed with prostate cancer.
    • 125/857 (14.6 percent) were biopsied and had negative prostate biopsies.
    • 436/857 (50.9 percent) were controls.
    • 27 percent self-classified as African Americans.
    • 73 percent self-classified as European Americans.
  • The average (median) age of all patients was 63 years.
  • Among the African American males
    • The average (median) genetic West African ancestry proportion was 0.78 .
    • The average (median) genetic Native American ancestry proportion was 0.04.
    • There was no significant difference in genetic West African ancestry among the men with and without a diagnosis of prostate cancer (p = 0.54).
    • Genetic Native American ancestry was significantly lower among the men with a diagnosis of prostate cancer (median 0.034 vs. 0.057, p = 0.03) compared to controls.
  • Among the European American males
    • The average (median) genetic Native American ancestry proportion was 0.067.
    • Genetic Native American ancestry was significantly lower among the men with a diagnosis of prostate cancer (median 0.04 vs. 0.08, p < 0.001) compared to controls.
  • On logistic regression analysis,
    • African Americans with a genetic West African ancestry of ≥ 88 percent had an increased risk of prostate cancer diagnosis (odds ratio [OR] = 2.6).
    • African Americans in the highest quintile for genetic Native American ancestry had a decreased risk of prostate cancer diagnosis compared to men in the lowest quintile (OR = 0.5).
    • European Americans in the highest quintile for genetic Native American ancestry had a decreased risk of prostate cancer diagnosis compared to men in the lowest quintile (OR = 0.3).

According to Nyame et al., their study reveals that

  • Genetic Native American ancestry is protective against prostate cancer diagnosis among all men.
  • African-American men with a high degree of genetic West African ancestry exhibit an increased risk of prostate cancer diagnosis.

8 Responses

  1. i think you mean “ethnic”.

  2. Correct … and fixed!

  3. Also BRCA gene may play a role.

  4. Dear Brainyblogger:

    Many other genetic factors certainly play a role in risk for diagnosis with prostate cancer. A family history of carriage of the BRCA1/2 genes is one example of one such genetic risk factor. However, that isn’t the point of this presentation. What is fascinating in this paper is that such a small percentage of Native American genetic ethnic ancestry can significantly reduce risk.

  5. It seems that the pure ubiquity of prostate cancer as one naturally ages dramatically overshadows any of the other possible contributing factors. Ethnic ancestry, diet, stress, and all the other factors, controllable or not, seem secondary to age (largely supported by the autopsy studies of men who died in accidents). Will you comment on this, please, so that the broader perspective considered?

  6. Age is quite certainly the dominant risk factor for diagnosis of all forms of prostate cancer. However, we now know that many prostate cancers being diagnosed today in men > 55 years of age may never need treatment because they are low risk and are not going to lead to the patients’ deaths.

    The interesting and perhaps less well understood question is the degree to which age is a key factor in the diagnosis of the higher-risk forms of prostate cancer that are clinically significant and might lead to prostate cancer-specific death. In such patients, age is certainly a key factor, but we really don’t yet know if it dominates risk in the same way that it does in all patients being diagnosed today.

  7. My husband was 66 at the time of diagnosis — Stage IV, metastatic (lymph nodes and bones involved). Wonder why he got this? The only thing we have found is that his mother had breast cancer.

  8. Dear Elle:

    We have no idea (yet) exactly why the vast majority of men get prostate cancer at all, let alone the more aggressive, clinically significant types of prostate cancer like your husband. The fact that his mother had breast cancer is actually relatively unlikely to be significant unless she had a genetic subtype of breast cancer known as BRCA1 or BRCA2, and she then passed that particular gene down to he son (which happens sometimes, but not all the time).

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