A total of 1008 white American, 581 African American, and 75 Ghanaian women contributed to this study. The mean age at the time of the diagnosis for Ghanaian women was 48.0 years (±6.4 years) compared with 60.7 years (±13.7 years) for African American women and 62.4 years (±13.7 years) for white American women (P = .0019). () All of the Ghanaian women had palpable cancers that were diagnosed by clinical breast examination followed by subsequent pathologic confirmation via freehand (ie, without image guidance) percutaneous core needle biopsy (⅓) or surgical resection (⅔). Mean primary breast tumor size for the Ghanaian, African American, and white American women was 3.20 cm, 2.3 cm, and 1.95 cm, respectively (P < .001). Approximately 75% (n = 56) of the Ghanaian cases were grade 3 lesions. Data for histologic grade were available for a total of 828 white American and 450 African American women. Of these women, 44.9% (n = 202) of African American and 29.3% (n = 243) of white American women were presented with grade 3 cancers ().
Comparisons of Clinicopathologic Features in Study Populations
A total of 57 (76%) Ghanaian women were diagnosed with ER-negative cancers. Data on the status of PR and HER-2/neu biomarker were available for a total of 48 women, of whom 66.7% (n = 32) were diagnosed with PR-negative and 95.8% (n =46) with HER-2/neu–negative breast cancers (). Data on the status of ERs were available for 995 white American and 576 African American women. The prevalence of ER-negative cancer was 21.9% (n = 218) in white American and 36.1% (n = 208) in African American women. We were able to retrieve PR data for a total of 827 white American and 443 African American women. Twenty-nine percent (n = 249) of white American and 43.4% (n = 199) of African American women were diagnosed with cancer lacking the expression of PRs. Finally, data for HER-2/neu bio-marker were available for a total of 836 white American and 442 African American women. More than ¾ (76.7%; n = 641) of white American women and 75.1% (n = 332) of African American women were diagnosed with HER-2/neu–negative breast cancer (). We then classified the 3 groups of women by the joint expression of the 3 diagnostic biomarkers (ER, PR, and HER-2/neu). We observed the highest prevalence of triple-negative breast cancers in Ghanaian women (82.2%, n = 37), followed by African American (26.4%, n = 107) and white American (16.0%, n = 122) women. In contrast, the highest proportion of women diagnosed with ER+ and/or PR+, HER2+ breast cancers was observed in white American women (61.9%, n = 472), followed by African American (49.4%, n = 200) and Ghanaian (13.3%, n = 6) women. ().
To minimize the potential confounding effect of advanced stages and poorly differentiated grades, we stratified American women by their stage and grade of cancers and estimated the prevalence of hormone receptor-negative breast cancers. A total of 28 (2.8%) white American women, 46 (7.9%) African American women, and 57 (76%) Ghanaian women were diagnosed with poorly differentiated and advanced stage (III/IV) breast cancer (). Absence of expression of ERs was observed in 77.2% (n = 44) of Ghanaian women, 67.4% (n = 31) of African American women, and 50.0% (n = 14) of white American women (P = .043). Interestingly, African American women had the highest prevalence of PR-negative cancers (76.1%, n = 35), followed by Ghanaian (69.2%, n = 27) and white American (60.7%, n = 17) women (P = .297). Finally, 94.7% (n = 36) of Ghanaian women were diagnosed with HER-2/neu–negative breast cancer, compared with 63.0% (n = 29) of African American women and 46.4% (n = 13) of white American women (P < .0001) (). We then stratified women by the joint expression of ER, PR, and HER-2/neu bio-marker (). Eighty-three percent (n = 30) of Ghanaian women were diagnosed with triple-negative breast cancer, whereas the proportion of African American women with triple-negative breast cancer was 41.9% (n = 18) and of white American women was 15.4% (n = 4). In contrast, white American women experienced the highest proportion (38.5%, n = 10) of hormone-independent, HER-2/neu–positive breast cancer, followed by African American (30.2%, n = 13) and Ghanaian women (2.8%, n = 1).
Comparisons of Clinicopathologic Features in Study Populations Subsets With Advanced Stages and Poorly Differentiated Grades
Figure 1 Prevalence is shown of selected subtypes among white American, African American, and Ghanaian women diagnosed with palpable cancers and poorly differentiated histologic grade. Frequencies shown are for hormone receptor-negative, HER-2/neu-positive, and (more ...)
We also stratified African American and white American women by their menopausal status and compared frequencies of triple-negative breast cancers. Among premenopausal African American and white American women, the prevalence of triple-negative breast cancer was 32.3% and 25.2%, respectively. These proportions were significantly lower than the 82% triple-negative rate observed among the Ghanaian cases, the majority of whom were younger than the commonly used menopausal surrogate cutpoint of 50 years. Non–triple-negative tumors were rare among Ghanaian cases, regardless of age.