Breast Cancer in Black Women
Early Detection
The early detection of breast cancer has traditionally involved three components of an age-specific examination: monthly self-examination of the breast, yearly clinical examination of the breast by a health care provider, and yearly mammography. In recent years, several large studies have examined the demographic characteristics of breast cancer screening participation, including knowledge of appropriate screening behavior, use of screening tests, and barriers to receiving the recommended breast cancer screening. These studies have helped to identify the particular needs of the black community in the United States.
Monthly breast self-examination has been recommended for all women 20 years of age and older, although the benefit of this on mortality from breast cancer has never been documented in a randomized trial. Reported rates of monthly breast self-examination range from 25% to 70%; the lower numbers come from reports in the early 1980s, and the higher figures come from more recent studies [33-35]. The use of breast self-examination by black women appears to be at least as high as that in white women, and in some studies it is higher (70% compared with 62% in the National Health Interview Survey from 1987). None of these studies has assessed knowledge of appropriate technique or training in breast self-examination; both of these factors are clearly related to the accuracy of this intervention.
Clinical breast examination by a health care professional has also not been studied as a single intervention in a randomized trial. It has, however, been a component of many of the mammographic screening trials that have documented a survival benefit associated with the use of breast cancer screening and has thus become an important part of the recommended cancer screening guidelines. Recent studies assessing the use of yearly clinical breast examination by women older than 40 years of age have found that 40% to 70% of women interviewed comply with this guideline. Race has not had an independent effect on the likelihood of obtaining a clinical breast examination, but women with lower incomes and less education have consistently had lower screening rates. This effect is particularly important for black women, because they may be disproportionately represented in these groups.
Yearly mammography in women older than 50 years of age is the cornerstone of the breast cancer screening effort in the United States. Mammography use has increased substantially during the last decade; the most recent surveys document an increase among both black and white U.S. women. Six studies in the last 7 years have assessed the effect of race on the use of mammography. Four of the six found no difference in the use of mammography between black and white women. The two reports that did find lower use of mammography among black women did not control for income level, which is a clear discriminating factor in most studies of mammography use. Thus, the lower rates of use identified in black women may result from financial barriers more than from societal or health care barriers.
Demographic characteristics that predict low rates of mammography use include increasing age, low income level, low level of education, rural residence, and lack of health insurance. In addition to these documented demographic findings, surveys of the target population for mammography have identified several important barriers to the regular use of mammography. In black women, the most commonly cited reasons for not having mammography are a belief that mammography is not needed if no clinical breast problems are present, the failure of a physician to recommend the procedure, the cost of the procedure, and a knowledge deficit about the increasing risk for breast cancer with age . These barriers are the same as those mentioned by white women, although black women more frequently cite lack of physician recommendation as an important reason for not obtaining yearly mammography.
Two clinical trials designed to increase breast cancer screening use have specifically targeted black women. Mandelblatt and colleagues used a nurse practitioner to recruit all women attending a public general internal medicine clinic who were 65 years of age or older to participate in breast, cervical, and colorectal cancer screening during their normally scheduled clinic visit. Seventy-one percent of the women approached agreed to participate, and two thirds of these women had mammography. Because only 8% of the eligible population had received a recent mammographic examination, this showed a substantial increase in recommended screening behavior. In a second study by Skinner and colleagues, women attending a family practice clinic were interviewed about their breast cancer screening behavior and beliefs. A letter individually tailored to their responses was then sent to half of the women; the other half received a standard form letter describing the importance of mammography. Although the tailored letter did not have a greater effect than the standard letter on the group as a whole, subgroup analysis found that black women and women with lower incomes responded positively to the tailored message. These two studies suggest that intervention by health care providers can significantly improve short-term compliance with breast cancer screening guidelines by black women. Studies examining adherence to repeated screening at the recommended intervals have not been reported.
Clinical Presentation
Large population-based studies have repeatedly shown that black women have breast tumors at a more advanced stage at the time of diagnosis. Black women have larger primary tumors, a higher incidence of spread to the axillary lymph nodes, and more distant metastatic disease than white women. The most striking difference is in the proportion of tumors that are node negative—53% of white and 42% of black women in the United States present with disease confined to the breast. Because lymph node involvement is the most important indicator of prognosis, this discrepancy becomes particularly important when the previously mentioned differences in survival rates are considered. It is important to note, however, that the absolute number of axillary lymph nodes involved with cancer in women with regional disease is not clearly different in black and white women. Although these findings have been consistent over time, a trend can be seen in the last 15 years toward the diagnosis of disease at an earlier stage in black women, possibly as a result of increased screening activity. The incidence of breast tumors that are not invasive (carcinoma in situ) or that are invasive but small (
< 2 cm) and confined to the breast, has increased by 100% to 200% in both blacks and whites during this time, although white women still present more frequently with early-stage disease.
Breast cancer histology is similar in black and white women; most cases consist of infiltrating ductal carcinoma. Several studies [31, 51, 60-62] have found a slightly higher incidence of medullary carcinoma in black women than in white women (7% compared with 3%), but this has not been a consistent finding. Most comparative studies have also found a higher incidence of poorly differentiated tumors in black women and an increased frequency of nuclear atypia, higher mitotic activity, and tumor necrosis [50, 62].
The higher frequency of poorly differentiated tumors in black women is compatible with the finding of a higher frequency of hormone receptor-negative tumors in black women, both in the United States and in South Africa [51, 54-56, 63-66]. Most investigators find that 60% to 80% of white women with breast cancer have estrogen receptor-positive tumors; the corresponding number for black women is 40% to 60%. Similarly, black women are less likely to have progesterone receptor-positive breast tumors, although this characteristic has been less widely studied [31, 55, 66]. Because postmenopausal women are more likely to have hormone receptor-positive tumors, some of the reported racial differences in estrogen and progesterone receptor levels could be the result of the younger median age of black women with breast cancer. Examination of this factor shows a persistent difference in hormone receptor levels between black and white women when they are separated by menopausal status [51, 67]. Both premenopausal and postmenopausal black women have a lower frequency of estrogen receptor-positive tumors than do corresponding white women.
Elledge and colleagues [55] have examined some of the more recently identified markers of breast tumor biology, including DNA ploidy, S-phase fraction (an index of tumor proliferation), HER2/neu protein levels (an oncogene product), and p53 protein accumulation (the product of a tumor suppressor gene). Their retrospective study involved 6678 white, black, and Hispanic women and found that the only difference between black and white women was in the S-phase fraction. White women had a significantly lower S-phase fraction than either the black or Hispanic women. This finding is not unexpected given the higher frequency of poorly differentiated tumors in black women.
Attempts to explain the above-described differences in clinical presentation and pathology of breast tumors have centered on an exploration of the effect of socioeconomic status on tumor stage at diagnosis and on tumor biology. It has been documented that women of lower socioeconomic standing have more advanced breast cancer at the time of diagnosis [54, 68-71]. Uninsured women and women who rely on public assistance to finance their medical care appear to have greater barriers to accessing that care for nonemergent problems [72]. As a result, some investigators have found that poorer women with breast cancer have a longer symptomatic period before seeking medical attention [73, 74]. Because black women are disproportionately represented in the lower socioeconomic strata, economic factors may explain the advanced disease in this population. Unfortunately, few studies have attempted to address this issue scientifically, and the results of these studies have generally conflicted [54, 68, 69]. It does appear, however, that black women seek medical attention for breast symptoms later than white women, even when socioeconomic status is considered [74]. This difference in symptom duration between black and white women is small (2 days) and seems unlikely to explain the substantial difference in stage at diagnosis that is seen between black and white women. Finally, socioeconomic status, through its effect on nutrition and environmental exposures, may also affect breast tumor histology. Chen and colleagues [62], who examined this issue in black women, found that socioeconomic or lifestyle factors could not explain the higher incidence of poorly differentiated breast cancers in black women.