Breast Cancer Race Differences Have Link to Vitamin D Gene ...

? Breast Cancer news ? Apr 09, 2012

Genetic variation in the vitamin D pathway might be part of the reason African-American women tend to have more aggressive breast cancer than those of European ancestry, researchers reported.

In a case-control study, two variants in a gene that plays a role in vitamin D metabolism were significantly associated with an increased risk of estrogen-receptor (ER) negative breast cancer in African-American women, according to Song Yao, PhD, of Roswell Park Cancer Institute in Buffalo, and colleagues.

But the same variants had no effect in women of European ancestry, Yao and colleagues reported online in Breast Cancer Research.

American women of African ancestry are more likely to have ER-negative breast cancer than those of European ancestry, the researchers noted. They also tend to have low levels of circulating 25-hydroxyvitamin D, the major metabolite of and a marker of vitamin D status, which in women of European ancestry is associated with ER-negative tumors.

Yao and colleagues thought that racial differences in 25-hydroxyvitamin D (25OHD) - as well as genetic variation in the vitamin D pathway - might contribute to observed differences in tumor characteristics.

To test the idea, they enrolled 1,771 women in a case-control study, in which they measured serum 25OHD levels and tested associations between risk and variation in three genes: one for the vitamin D receptor and two others involved in vitamin D metabolism, CYP24A1 and CYP27B1.

Breast Cancer, Race, and Ethnicity

Breast cancer is one of the most common cancers affecting American women, and is second only to lung cancer as a leading cause of cancer death in women. The number of breast cancer cases (incidence) has been on the rise during the past 20 years, while the death rate from breast cancer has decreased slightly in the past five years. The increase in cases is related, in part, to a greater emphasis on screening with routine breast exams and mammography.

These screening tools often can detect breast cancer at an earlier - and more treatable - stage, which helps explain why the death rate has not increased significantly.

Does Race or Ethnicity Affect Breast Cancer Risk?

All women should be aware of their risk for breast cancer; it can affect women of every age, race, and ethnic group. However, the rates of developing and dying from breast cancer vary among various racial and ethnic groups.

According to the National Cancer Institute, white, non-Hispanic women have the highest overall incidence rate for breast cancer among U.S. racial/ethnic groups, while Korean American women have the lowest rate. Among women ages 40-50, African American women have a higher incidence of breast cancer than white women. African American women also have the highest death rate from breast cancer; Chinese American women have the lowest death rate.

Several factors have been found to impact the breast cancer incidence and death rates among racial and ethnic groups. Differences in certain lifestyle behaviors - such as diet, exercise, and acceptability of smoking and alcohol use - can impact the risk of many diseases, including heart disease and breast cancer.

The higher death rate from breast cancer among African American women has been linked to the stage, or extent, of the cancer at the time it?s diagnosed. Studies show that African American women tend to seek treatment when their cancer is in a more advanced, less treatable stage.

All told, 928 women in the study had breast cancer, including 547 African Americans and 381 women on European ancestry. In the control group, 461 and 382 women were of African and European ancestry, respectively.

Because treatment for breast cancer can affect vitamin D levels, that aspect of the research was analyzed in the control group, where African Americans, on average, had serum 25OHD levels of 14.9 ng/mL, compared with 21.4 in those of European ancestry. The difference was significant at P

The analysis also showed that 34.3% of African Americans in the study had severe vitamin D deficiency, defined as a serum 25OHD level of less than 10 ng/mL. In contrast, only 5.9% of women of European ancestry had severe deficiency.

In the overall study population, the researchers found, single nucleotide polymorphisms?single base pair changes?differed by race.

Provided by ArmMed Media

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