Treatment

A few studies have evaluated the treatment of breast cancer in black women. Several studies from the 1980s [52, 75] suggested that black women were less likely than white women to have surgical therapy for local or regional disease. These studies failed to adequately consider local tumor characteristics, such as skin involvement and direct extension of the tumor outside of the breast, that could have contributed to treatment decisions. More recently, the Black/White Cancer Survival Study Group [76] reported that among women with equivalent cancer stage, black women were just as likely as white women to have surgical therapy as part of their primary treatment plan. The group found that black women were less likely to have breast-conserving surgery and more likely to have a modified radical mastectomy. However, when tumor size and comorbid conditions such as diabetes mellitus and hypertension were considered, race was not found to be a significant predictor of breast-conserving surgery. The results of treatment with conservative surgery followed by radiation therapy in black women appear to be similar to those seen in the population as a whole. No difference has been documented in local failure rates between black and white women (5% and 8%, respectively), and cosmetic results have been considered good to excellent in more than 80% of women of both races [77].

The use of systemic adjuvant therapy, either chemotherapy or endocrine therapy, has generally not been found to vary significantly according to race, although the data in this area are limited [50, 55, 76, 78]. Even less information is available about the efficacy of systemic therapy in preventing relapse or improving survival rates in black women with breast cancer. One study [79], presented only in abstract form, suggested that black women enrolled in Eastern Cooperative Oncology Group chemotherapy studies for breast cancer had worse survival than matched controls, but not enough information was presented to adequately analyze the reported findings. Similarly, the Piedmont Oncology Group [80] found that although the response of black women with metastatic breast cancer to chemotherapy was similar to that of white controls, the survival rate of black women was significantly shorter. Comorbid conditions and socioeconomic variables that may have affected survival were not analyzed.

Outcome

The relative 5-year survival of black women with breast cancer in 1990 was 64%; the corresponding rate for white women was 80% [1]. Although a steady improvement in the 5-year survival rate has been documented in both races since 1960, the difference in the proportion of black and white women surviving has remained relatively stable. This substantially higher case-mortality rate for black women has resulted in a higher age-adjusted breast cancer mortality rate for black women in the United States, despite the lower incidence of cancer in this population (Figure 3). More advanced stage at diagnosis, differences in tumor biology, treatment differences, sociodemographic issues, and the presence of comorbid illnesses have all been suggested as factors contributing to the poorer survival of black women with breast cancer.

Figure 3. Age-adjusted breast cancer mortality rates. Data obtained from Miller and colleagues [1].

Tumor stage is the most important determinant of outcome in women with breast cancer, and it is well documented that advanced stage disease is more common in black women. Therefore, many investigators have felt that the poorer survival rates seen in black women result from the difference in the stage distribution of breast tumors at the time of diagnosis. Adjustment for stage of disease generally narrows the survival difference but frequently does not eliminate it [49, 50, 55, 81, 82]: A disparity in survival rates tends to persist when women of the same stage are compared (Figure 4).

Several groups [50, 55, 71, 81] have found that black and white women with disease in a very early stage (lymph nodes not involved with cancer) and women with metastatic disease have similar survival; those with intermediate prognosis disease (local or regional disease and lymph nodes involved with cancer) continue to show a disparity in survival.

Figure 4. Five-year relative survival rate by cancer stage at diagnosis. Measurements in centimeters refer to the size of the primary tumor. N+ = lymph nodes involved with cancer; N– = lymph nodes not involved with cancer. Data obtained from Swanson and colleagues.This raises the possibility that treatment differences may also play a role in the outcome disparity, because adjuvant treatment has its greatest absolute effect on women with local or regional disease and lymph nodes involved with cancer. As discussed earlier, little information is available about treatment patterns in black women, especially about the use of adjuvant chemotherapy and the efficacy of such treatment in this population. In one large population-based study [82], treatment variation did not substantially contribute to the survival differences seen between black and white women.

The previously described differences in breast tumor biology seen in black women could also contribute to the disparity in survival. Women with poorly differentiated tumors, hormone receptor-negative tumors, or tumors with a higher S-phase fraction have all been shown to have a worse prognosis than women with tumors without these characteristics [83-90]. The Black/White Cancer Survival Study [82], the most comprehensive study of racial survival differences in breast cancer to date, found that tumor biological characteristics (tumor grade and hormone receptor status) were second only to tumor stage in contributing to the survival difference. In addition, several groups [56, 91] have found that estrogen receptor status is a particularly strong prognostic indicator in black women, especially postmenopausal black women. The few studies [55, 92-94] that have evaluated more recently identified markers of tumor biology that may affect prognosis have reported conflicting results, and further information is clearly needed before the importance of these markers as prognostic indicators in black women can be assessed.

Underlying medical conditions could adversely contribute to overall health or prevent the delivery of optimal therapy for breast cancer, and they have also been implicated in the worse outcome of black women with breast cancer. Several investigators [50, 95, 96] have found an unusually high risk for death from other causes in black persons or uninsured persons with cancer. The Black/White Cancer Survival Study Group found that black women with breast cancer were significantly more likely to have serious underlying medical problems (diabetes, hypertension, heart disease, lung disease, or kidney disease) than a matched population of white women. Sixty-seven percent of white women were free of underlying medical problems compared with 44% of black women. Black women were also more likely to be overweight and to have markers of poor nutritional status (high body mass index and low serum albumin levels, hemoglobin levels, and lymphocyte counts) [53]. Most investigators have found that such comorbid conditions contribute modestly to the worse prognosis for survival in black women with breast cancer [50, 53, 82].

The most difficult issue to clarify is the contribution of socioeconomic status to the worse survival seen in black women with breast cancer. It is not hard to understand why economically disadvantaged women may present with disease at a more advanced stage, may be at higher risk for receiving suboptimal therapy, are more likely to have important underlying comorbid medical conditions, and may even have some differences in tumor biology. General conclusions that can be drawn from the existing data include a strong association between race and socioeconomic status and an apparent correlation of socioeconomic status with worse survival in persons with cancer [53, 56, 71, 82, 95, 97, 98]. Of the five studies that have tried to directly measure the effect of socioeconomic factors on the worse survival of black women with breast cancer, two [56, 97] have found that socioeconomic factors combined with tumor stage completely explain the racial difference in survival, and the other three [73, 82, 98] found that although social and economic factors contributed to survival differences, they could not completely explain them. It appears that the worse prognosis of black women with breast cancer cannot be explained by any single factor but results from a complex interaction of many issues, including tumor stage, tumor biology, comorbid conditions, and socioeconomic variables.