Patterns and Outcomes of De-novo Metastatic Breast Cancer Based on the Various Molecular Subtypes at the Kenyatta National Hospital

Abstract

Background Breast cancer is the most frequently diagnosed malignancy among women. Globally, it ranks as the fourth leading cause of cancer-related mortality. In Kenya it is the second primary cause of cancer-associated deaths. A significant proportion of Kenyan patients are diagnosed at advanced stages, with a notable percentage presenting with de novo metastasis, this contributes to adverse prognoses. Purpose: To determine the patterns and outcomes of de-novo metastatic breast cancer based on the various molecular subtypes. Methodology: We conducted a retrospective cohort study on patients seen at the Kenyatta National Hospital Cancer Treatment Centre (CTC) between 2018 and 2019 among adult female patients with de-novo metastatic breast cancer. We reviewed the patients' records consecutively with 157 meeting the inclusion criteria and captured the data using a structured questionnaire. Data analysis was done in R version 4.1.2. Kaplan-Meier analysis was performed to determine the survival of patients at three years of follow-up. Factors associated with mortality were assessed using Cox Proportional regression. The results were presented using p values and hazard ratios. Results were interpreted at 5% significance level. Results: The median age of the patients was 45 years with an interquartile range of 39 to 53 years. Most of the patients, 140 (89.2%) complained of breast mass at diagnosis. A total of 150 (95.5%) had invasive ductal carcinoma. ER/PR positive, HER2 negative was the most prevalent receptor subtype, 65 (41.4%). The majority, 88 (56.1%) of the breast cancers were grade 2. The most common site of metastasis was the lungs, 79 (50.3%) followed by bones at 70 (44.6%). The overall survival rate at the three-year follow-up was 37.1%. Patients with ER/PR positive, HER2 negative receptor subtype had the highest survival rate at 53.5%. ECOG performance score was significantly associated with mortality at 3 years (P<0.05), HR 2.9 (95% CI 1.27, 6.63). Conclusion: The lung was the most affected site of metastasis. The overall survival rate at 3 years was low as revealed by the results. Patients with ER/PR positive, HER2 negative receptor subtype had better survival rates. ECOG performance status can be used to predict mortality among patients with de-novo metastatic breast cancer