The breast cancer death rate among American women has dropped, apparently reflecting the effects of early detection and treatment, according to new statistics released Tuesday by the National Cancer Institute.

The decline was especially pronounced among white women in the 1990s, reversing an upward trend from the previous decade, the institute said. Increases in the death rate have continued for black women, but, even in this group, the overall increase has slowed significantly, the NCI said.

The American Cancer Society has estimated that 44,300 women will die of the disease in 1996, “but that estimate could prove to be too high if the trend continues,” the institute said in a statement.

Breast cancer is the most commonly occurring cancer in women - a projected 184,300 new cases will be diagnosed this year - although lung cancer is the leading cancer killer of women.

Between 1989 and 1993 - the most recent five-year period of available data - the age-adjusted breast cancer mortality rates declined about 6 percent among white women and rose about 1 percent in black women.

Between 1980 and 1989, rates had increased 3 percent for whites and 16 percent for blacks, the NCI said.

Overall, the breast cancer death rate for U.S. women has fallen about 5 percent in recent years, dropping from 27.5 per 100,000 women in 1989 to 25.9 in 1993, the institute said.

Racial differences in mortality rates likely were related to several factors, including the risk of developing breast cancer, and access to detection and treatment, the NCI said.