In this study, African American women with later-stage disease at diagnosis and those with negative ER/PR hormone receptor status were at increased risk of mortality compared with European American women. The study is unique in that it examines mortality experiences in a group of women who, due to their socioeconomic status, were shown to have longer delays between detecting a breast abnormality to diagnosing breast cancer and between diagnosis to treatment initiation (8
). Both of these delays impact stage at diagnosis and breast cancer outcomes, whereby women with delayed evaluation and treatment are more likely to be diagnosed at a later stage and ultimately experience a higher risk of mortality (15
). Additionally, the BCN participants studied represent two racial groups that, in previous studies, exhibited a difference in time-delay intervals, breast tumor characteristics, and cancer mortality (27
). Thus, our finding that delays were not different between African American and European American women is particularly encouraging and interesting. The finding that race and total delay were not significant independent risk factors for breast cancer survival in our study suggests that the targeted efforts seen through the BCN to an otherwise high-risk group is proving beneficial in shortening the racial disparity gap in breast cancer mortality. This is a testament to the National Breast and Cervical Cancer Early Detection Program, whose aim is to assure equal access to timely and quality cancer screening and diagnosis among medically underserved women.
By contrast, the molecular markers of ER/PR that were found to impact mortality and shown to differ by race indicate an etiologic difference in tumor aggressiveness by race. As such, they cannot be controlled through interventions aimed at early detection, diagnosis, and treatment. This study contributes to a growing body of research, including those conducted in South Carolina, that have also noted differences in the presence of prognostic molecular markers by race such that African American women are significantly more likely to have ER/PR – negative tumors than European American women, even after controlling for tumor stage (41
). For example, Cunningham found that in South Carolina, African Americans had more aggressive diseases with ER-negative tumors compared with their European American counterparts (42
). On a national level, using the Surveillance, Epidemiology, and End Results database, Morris and colleagues observed that African American women were more likely to have ER-negative tumors and breast cancers found at later stage and higher grade (47
). It is interesting to note the significant interaction between race and ER/PR receptor status that was noted for all-cause, but not disease-specific, survival. Further studies are needed to understand the interaction between race and hormone receptor status. These findings may have implications for basic/etiologic research as well as for targeted cancer treatment.
In the analyses of factors influencing the exposure-delay intervals and mortality, stage of disease was significantly associated with the risk of mortality. This result was observed when deaths were attributed to all-cause mortality and when deaths were attributed to breast cancer, further highlighting the impact that disease stage plays on survival. The HR increased in all breast cancer –specific survival analyses when the interaction term between race and hormone-receptor status was included in the model. The most pronounced increase in the HR for stage was seen in the model that considered treatment delay as the main exposure in which the hazard increased from 3.7 to 4.6.
Researchers have found that African American women have longer delays than European American women whereas other researchers did not note a significant difference (26
). Thus, diagnosis and treatment delays may be affected by other factors. Psychosocial factors, such as having higher levels of cancer-specific anxiety, fatalistic beliefs, misconceptions about cancer, cultural beliefs, and sociodemographic variables also have been found to influence patient delay (39
). Sociodemographic factors include having a low household income, poor health status, no history of previous screening mammographies, and transportation problems (36
Our study has several limitations. Data quality was not assessed on ER/PR status and treatment type, and interpretation of the study findings needs to be made in lieu of this limitation. We were unable to identify ER/ PR status on 42% of the women and treatment type on 10% of the women. ER/PR information is not required to be reported to the SCCCR. The women without ER/PR status, however, did not differ significantly from those with ER/PR status on important background factors such as race, treatment type, income, or tumor stage. In further examination by hospital type, a comparison of American College of Surgeons – approved hospitals versus non – American College of Surgeons hospitals showed no differences in reporting ER/PR or treatment type. After further analysis, treatment type did not differ between African American and European American women. Furthermore, the type of treatment was not different by tumor type, size, or stage. The type of treatment, however, did differ by tumor grade, with persons having poorly/undifferentiated tumors being more likely to receive chemotherapy/radiation and surgery compared with persons having well/moderately differentiated tumors. No treatment or an unknown treatment type was more likely to be found among women with unknown ER/PR status compared with women with known ER/PR status.
Information regarding other factors that have been shown to impact the risk of breast cancer, such as parity, menopausal status, body mass index, the presence of BRCA1
, and age at menarche also were not available (56
). Similarly, information concerning her-2/ neu, a known prognostic risk factor for more aggressive breast cancer and a marker for resistance to adjuvant therapy that is associated with breast cancer recurrence and mortality, also was not available (57
). Her-2/neu expression and ER/PR status act as prognostic factors for breast cancer and, taken together with other known effects on breast cancer recurrence and mortality, may have impacted our study (62
). Another limitation of our study is the possibility of residual confounding due to the collapsing of small cell frequencies found among some variables, particularly stage and grade of disease. This could have resulted in some confounding factors not being accounted for in the model.
On the other hand, our study has several strengths. To our knowledge, this is the first study to examine racial disparities, the timeliness of diagnosis and treatment, and their collective effect on mortality among medically underserved women. Although the results of the present study may not be generalizable to other programs due to demographic differences, the findings can inform other organizations and programs aimed at targeting patients who are economically disadvantaged and from racial minority groups. Also, it may have special relevance to the 55% of all African Americans who live in the Southeast.
In summary, these findings suggest the usefulness of targeted efforts through programs, such as the BCN, to ensure prompt follow-up of breast abnormalities and treatment initiation among economically disadvantaged women and racial groups. Additionally, these findings highlight the need for future research into the etiology of racial differences, particularly regarding prognostic molecular markers, and their impact on the survival of patients with breast cancer.