Black American women are more likely to have a hard-to-treat form of breast cancer, they get it earlier and they are more likely to die of it, researchers said on Thursday.

Their findings, presented at a breast cancer conference in San Francisco, support other studies that show clear ethnic differences in breast cancer that are likely to be genetic in origin.

The findings held regardless of a woman’s income, education or insurance coverage, Dr. Catherine Lee of the University of Michigan Comprehensive Cancer Center said.

“We found overall that African-Americans are diagnosed at younger ages and at more advanced stages than their white American counterparts,” Lee told reporters in a telephone briefing.

Blacks are also far more likely to have a form of cancer called estrogen receptor-negative cancer - the type that is not helped by estrogen-based drugs such as tamoxifen.

Lee’s team analyzed data on 170,079 cases of breast cancer from 1,600 hospitals in all 50 states. White women accounted for 90 percent of the cases, with black women making up nearly 10 percent.

Thirty-nine percent of black women had ER-negative tumors, compared with 22 percent of white women. Black women were diagnosed at an average age of 57, compared to 62 for white women, yet their cancer was more advanced, with just 29 percent having stage 1 tumors that had not spread yet, compared to 42 percent of white women.

The findings bolster a growing body of evidence that shows breast cancer is different biologically in African-American women, Lee told the Breast Cancer Symposium, co-sponsored by the American Society of Breast Disease, the American Society of Breast Surgeons and other groups.

“Differences in tumor biology have a significant impact on survival,” Lee said in a statement.

“The fact that breast cancers in black women are more aggressive biologically suggests that we need to focus more of our research energy on developing better treatments targeting ER-negative tumors,” she added.

“These findings also point to a need for improved cancer education and screening in black women, particularly those in younger age groups.”

Breast cancer is the second most common cancer killer of women, after lung cancer. It will be diagnosed in 1.2 million people globally this year and will kill 500,000.