A new study by Yale researchers has found that a genetic mutation related to more aggressive breast cancers is four times more common in African-American women than in white women.

While African American women have a lower overall incidence of breast cancer than white women in the United States, their cancers have a worse prognosis, growing more aggressively, developing at a younger age, and resulting a higher mortality rate. Yale scientists found the underlying biological explanation for the difference to be mutations of a tumor suppressor gene called p53.

The study was helmed by Beth A. Jones, assistant professor of epidemiology and public health at Yale School of Medicine, who focuses on racial differences in the incidence and mortality of cancer.

“Although these tumor mutations are present in a lot of human tumors, in breast cancer they’ve been associated with the worst prognosis … and they’ve been reported to impact, or modify, the response to therapy,” Jones said. She said there is some chemotherapy resistance in p53 positive breast cancers.

In examining the breast tumors of 145 African-American women and 177 white women, researchers found mutations of p53 four times more often in cancers found in African American women.

Previous explanations for the differences in cancer prognoses among races have dwelled on socio-economic status, access to health care, and other factors. However, Yale scientists attempted to control for these factors in their research and showed the mutation is still more common in African American women.

“We adjusted for the greater obesity in African-American women with breast cancer,” Jones said. “We adjusted for socioeconomic status … and some lifestyle factors. Taking all of that into account, we still saw that African-American women were more likely to have p53 alterations.”

The authors also confirmed prior findings that tumors in African-American women were more likely to display characteristics associated with poor prognoses. Jones said later-stage diagnosis, larger tumor size and lymph node involvement characterize breast cancers in African American women.

Jones said the results of the study suggest that African-American women should be vigilant in monitoring their health.

“We’re seeing a consistent picture of tumors in African-American women that are associated with more aggressive behavior, and we’ve known for a while that African American women tend to be diagnosed at younger ages than white women,” Jones said. “Given those factors … early detection is very important for African American women … It’s important to adhere to the more stringent [screening] guidelines.”

In the future, Jones will extend her research to include Hispanic and Latina women, a population that has been rapidly increasing in Connecticut and the United States.

Stanislav Kasl, professor of epidemiology and public health at the Yale School of Medicine, said future studies might include other cancers, like prostate and colorectal. In addition, researchers have received funding to examine different survival rates between races.

The study was funded by grants from the National Cancer Institute and the Department of Defense Breast Cancer Research Program. It will be printed in the journal Cancer on Sept. 15.