March 26 (Bloomberg) -- Low-income black and Hispanic women under 40 are at greater risk of contracting a particularly deadly form of breast cancer, a study said.

African-Americans were 1.77 times as likely to be diagnosed with this especially virulent strain as white women, and Hispanics were 1.23 times as likely, according to a study today in the journal Cancer.

The findings ``may help hasten the development of specific targeted therapy for this subtype of breast cancer,'' said the study led by Katrina Bauer, a research associate with the California Cancer Registry's Public Health Institute in Sacramento.

The severest form of the disease consists of so-called basal-like cancers that have none of the three tumor ``markers'' that can help physicians offer prognosis and proper treatment. These so-called ``triple negative'' tumors, which accounted for about 15 percent of all breast cancers, were typically diagnosed at more advanced stages than other tumors, the study said.

Women under 40 were 1.53 times as likely to be diagnosed with these unusually large, aggressive and fatal tumors as women between 60 and 69, it said. Low-income females were more likely to contract this disease than those in higher income brackets.

Among women with this most harmful strain, 77 percent survived five years after diagnosis, compared with 93 percent for those with other types of breast cancer, the study said. African- American women had the lowest survival rate of any ethnic group, with 14 percent alive five years after diagnosis.

The study used statistical analysis in looking at 51,074 California women diagnosed with different types of breast cancer between 1999 and 2003.

To contact the reporter on this story: Neil Roland in Washington at nroland@bloomberg.net

Last Updated: March 26, 2007 00:40 EDT