Impact of the molecular pathology of breast cancer on mortality rates and overall survival in a Haitian cancer clinic.

Abstract

e13588 Background: Breast cancer in the most common malignancy among women in Haiti and is mostly diagnosed at an advanced stage. While it is well known that molecular subtype is a prognostic factor, it needs to be investigated among Haitian patients with breast cancer. This study aimed to evaluate the impact of molecular classification of breast cancer on the survival of patients managed in Haiti’s largest cancer clinic. Methods: A retrospective study was conducted on the breast cancer patients of Innovating Health International (IHI) in Port-au-Prince, Haiti from January 2014 to December 2018. Chart review included all patients with breast cancer and tested for molecular classification. Data on variables such as date of admission, age, TNM staging, molecular classification, outcome and date of death were collected for the analysis. Mortality rate and median overall survival (OS) were estimated as of December 31st, 2019 and stratified according to molecular subtypes. Results: Among the 948 breast cancer cases diagnosed for the study period, 234 (24.7%) of them had a complete molecular classification. The mean age was 51.5 years [range: 23-94]. 55.1% of the patients were ER-positive, among them 33.7% ER+/PR+/HER2-, 15.4% ER+/PR-/HER2-, 2.1% ER+/PR-/HER2+ and 3.8% ER+/PR+/HER+ (triple positive). There were overall 25.6% of luminal A and 29.5% of luminal B cases. 44.9% were ER-negative, among them 14.1% ER-/PR-/HER2+ (HER2-enriched) and 29.1% ER-/PR-/HER2- (triple-negative). 92.2% of the patients had advanced breast cancer (stages IIB to IV). 29.5% had metastatic breast cancer, 22.8% for luminal A cases, 27.0% for luminal B, 36.7% for HER2-enriched and 32.8% for TNBC. Overall mortality rate was 42.3%, respectively 33.3% for luminal A cases, 37.7% for luminal B, 42.4% for HER2-enriched cases and 55.9% for TNBC. Median OS was not yet reached for luminal A, luminal B and HER2-enriched breast cancer, with a respective mean survival of 52.4 months, 51.3 months and 51.6 months. However, OS was 30.6 months for triple-positive breast cancer and 23.7 months for TNBC. Conclusions: Patients with luminal A breast cancer were less likely to have metastatic disease and thus had lower mortality rate and better overall survival. This was likely due to its less aggressive biology and the availability of hormone therapy. Poor availability and inaccessibility of HER2-targeted drugs were the main cause of the higher mortality rate among HER2-enriched patients. TNBC remains the most aggressive subtype.