The observed widened racial disparity of breast cancer mortality in Georgia is associated with increased incidence rate in black women and the disparity in cancer cell differentiation

B44 Introduction:It is known that black women have lower incidence rates, but higher mortality rates from breast cancer compared to white women. The explanations for this discrepancy are due to the differences in tumor response or access to newer medical interventions. >Method:We sorted all the 159 counties in Georgia according to the percentage of families with annual incomes less than $10,000 and classified them into 16 groups (about 10 counties in each group). We estimated the incidence rates for 1999-2003, the only available period in Georgia cancer registry, and mortality rates for 1994-2004 by races and percentages of low income families. >Results:The mortality rates from breast cancer declined 25.5% and 5.7% for black and white women, respectively, during 1994-2005. The black/white mortality ratio increased from 1.15 to 1.35 in this period. However, the incidence rate for black women increased 18.8% from 1999-2003, about 3.8% per year. The incidence rate for white women remains in the same level. The racial disparity in mortality increased, but it may be due to the significant increase in incidence rates in blacks. The black/white incidence ratio increased 18%, but mortality ratio increased only 11%, during 1999-2003. When we compare the mortality/incidence ratio to remove the impact of incidence on mortality, we found this ratio declined from 0.27 to 0.24 for blacks and from 0.16 to 0.15 for whites, indicating a greater improvement in survival of black female breast cancer cases. >Both incidence and mortality rates are inversely associated with the percentage of low income families in both races. The higher the percentage of low income families, then the lower incidence and mortality rates occur. The slopes for the percentage of low income families are -1.80 (R2 =0.47) and -1.44 (R2 =0.24) for incidence rates in black and white women, respectively, and are -0.68 (R2 =0.44) and -0.14 (R2 =0.17) for mortality rate in black and white women, respectively. In all 16 county groups, the incidence rates for black women are all lower than in corresponding white women, and the differences are significant in seven of the 16 groups. In contrast, the mortality rates in black women are all higher than in corresponding white women and the differences are significant in ten of the 16 groups. No significant differences in percentage of early diagnosis was found between black and white women in the 16 groups, but the percentage of well and moderately differentiated cancers in white women are significantly higher than in black women in 11 of the 16 groups. >Conclusion:The observed widened racial disparity in breast cancer mortality is due to the increased incidence rates in black women rather than differences in stage of diagnosis. The racial disparity can not be explained by lower social economic status of black women, because the significant lower incidence and mortality rates in both races were found in the areas with highest percentage of low income families. A worse grade of cancer cell differentiation may be one of the factors playing a role in disparity.