Prognostic features of breast cancer differ between women in the Democratic Republic of Congo and Belgium

ObjectivesCompared to European women, breast cancers in African women present at a younger age, with a higher tumor grade and are more often estrogen receptor (ER)/progesterone receptor (PR) negative. We here investigate the histopathological and immunohistochemical characteristics (ER, PR and human epidermal growth receptor 2 (HER2)) and the proportion of triple negative (Tneg) invasive breast cancers from an unselected series of patients diagnosed in Kinshasa, and compare them to a population of Caucasian women with a palpable breast cancer.Materials and methodsFrom 2010 till 2013, during the first breast cancer awareness campaign, organized in Kinshasa, 87 patients were diagnosed with invasive breast cancer. Diagnose was based on core biopsy. The control group consisted of Caucasian women (University Hospitals of Leuven, Belgium) with a palpable mass, diagnosed between 2000 till 2009, treated with surgery of which the histopathological and immunohistochemical characteristics were collected on excision specimens. Each patient in the Kinshasa group was matched based on age and tumor size to one or more patients of the Leuven database. Differences between both groups with respect to hormone receptors (ER, PR, HER2, Tneg) or grade are presented as relative risks (RR). The analysis is based on a log-binomial model accounting for clustering through matching by a random intercept for cluster. Differences between both groups with respect to hormone receptors correcting for grade is performed by the inclusion of grade as a covariate in the model.ResultsAfter adjusting for age, tumor volume and tumor grade, ER was more frequently negative (RR = 0.71, p < 0.001), with a trend in the same direction for PR (RR = 0.87, p = 0.057), and HER2 more often positive (RR = 1.60, p = 0.015) compared to the group from the University Hospitals of Leuven. There was no difference in the proportion of breast cancers being triple negative. Sub-analysis showed that the higher HER2 positive rate was only observed in older patients (≥50y: RR = 2.07, p = 0.007) whereas no difference in HER2 positive rate was found in younger patients (<50y: RR = 1.30, p = 0.358). A higher ER negative rate was observed in both age groups, however more pronounced in older patients (≥50y: RR = 0.64, p = 0.001; <50y: RR = 0.79, p = 0.018).ConclusionBreast cancer in women of Kinshasa presents at younger age and is more aggressive (more frequently ER negative and HER2 positive) compared to Caucasian women and this is more pronounced in older women (>50y). Only the ER results were concordant with the results of two similar studies (comparing an African with a European group), but were different when compared to studies on African-American women with breast cancer. This information is very important considering the treatment option: as more tumors are ER negative, endocrine therapy cannot be given while chemotherapy is often too expensive.