Breast cancer subtypes: implications for the treatment and survival of patients in Africa—a prospective cohort study from Mozambique

Abstract

BackgroundData regarding breast cancer epidemiology, treatment and survival in Africa are scarce. We aimed to assess the distribution of breast cancer subtypes in Mozambique and its impact on patients’ treatment and survival. The concordance of biomarker assessment between cytological and histological samples was also evaluated.MethodsProspective cohort study including 210 patients diagnosed between January 2015 and August 2017, followed to November 2019. Clinicopathological characteristics, treatment, 3-year overall survival (OS) and disease-free survival (DFS) were compared across classic tumour subtypes (oestrogen receptor (ER)-positive/human epidermal growth factor receptor 2 (HER2)-negative, HER2-positive and triple-negative breast cancer (TNBC)) and surrogate intrinsic subtypes (St. Gallen classification). Concordance was measured using Cohen’s κ statistics.ResultsA total of 51% of patients had ER-positive/HER2-negative tumours, 24% HER2-positive and 25% TNBC. Concordance between cytological and histological samples regarding ER and HER2 status was substantial (κ=0.762 and κ=0.603, respectively). There were no significant differences across subtypes regarding clinical characteristics and treatment, except for HIV positivity and high histological grade (more prevalent among TNBC) or endocrine therapy (higher use among ER-positive/HER2-negative and HER2-positive patients). Three-year OS was 52.5% (95% CI, 44.3% to 60.0%), being higher in ER-positive/HER2-negative (61.1%) compared with HER2-positive (53.2%) and TNBC (31.9%) patients. Adjusted HRs were 1.96 (95% CI, 1.13 to 3.39) among HER2-positive and 3.10 (95% CI, 1.81 to 5.31) among TNBC versus ER-positive/HER2-negative patients. Three-year DFS was 46.6% (95% CI, 38.0% to 54.8%), being lower among TNBC versus ER-positive/HER2-negative patients (HR 2.91; 95% CI, 1.64 to 5.16). Results were similar between surrogate intrinsic subtypes.ConclusionThere was a high proportion of HER2-positive and TNBC among Mozambican patients and their survival was poor compared with ER-positive/HER2-negative patients, partly due to the limited treatment options. A systematic assessment of ER, PR and HER2 status is feasible and may help tailoring and optimise the treatment of patients with breast cancer in low-resource settings, potentially leading to survival gains in this underserved population.

Survival Impact and Cost-Effectiveness of a Multidisciplinary Tumor Board for Breast Cancer in Mozambique, Sub-Saharan Africa

“…We conducted the prospective Moza-BC cohort study, which included consecutive patients with newly diagnosed breast cancer with a pathological diagnosis between January 2015 and August 2017 (supplemental online Fig. 1) [26]. Data on socio-demographic characteristics, risk factors, HIV status, clinical and tumor characteristics, treatment, and survival of patients treated in the oncology unit of the © 2020 AlphaMed Press Survival Impact of a Multidisciplinary Tumor Board Maputo Central Hospital were prospectively collected until July 2018.…”

Risk Factors for Breast Cancer, Overall and by Tumor Subtype, among Women from Mozambique, Sub-Saharan Africa

“…Likewise, we have no information on breast cancer family history among the controls, but as the proportion of cases with a positive family history was very low (4%), this may be of little relevance within this population. Around 25% of the cases were HIV-positive (27), but this information was not available for controls. Yet, although some U.S. studies have reported a lower incidence of breast cancer among women with HIV infection compared with the general population (64), African studies show no effect of HIV on breast cancer risk (65,66).…”

“…Still, an absence of effect in HR-negative tumors could be explained by the high adherence to breastfeeding among Mozambican women, which reinforces the need to promote this behavior-especially since the proportion of women with HR-negative and TNBC is already high in Mozambique (33% and 25%, respectively; ref. 27).…”

“…Cases were selected among women with breast cancer enrolled in the prospective Moza-BC cohort, previously described elsewhere (27). Briefly, it included a consecutive series of women with newly diagnosed primary breast cancer, with a pathologic diagnosis performed at one of the three Central Hospitals in Mozambique, from January 2015 to August 2017, which were the only hospitals with a Pathology Department at the time.…”

“…National guidelines for early breast cancer detection based on breast self-exam and clinical exam were implemented in 2010 (26), but there are no organized mammography screening programs, and women are usually diagnosed with advanced disease (stage III/IV; ref. 27).…”