Date of Award

2023

Document Type

Dissertation

Degree Name

Master of Medicine (MMed)

First Supervisor/Advisor

Dr. Khalid Makhdomi

Second Supervisor/Advisor

Dr. Samuel Nguku Gitau

Third Supervisor/Advisor

Dr. Sitna Mwanzi

Department

AKU-East Africa

Abstract

Introduction: Aromatase inhibitors (AIs) are a commonly used type of endocrine therapy for post-menopausal women with breast cancer. In clinical trials with a predominant Caucasian population, it has been shown to cause reduction in bone mineral density of up to 1.5% and 3.2% in total hip and 2.6% and 4% in lumbar spine after 1 and 2 years of AI therapy respectively. Previous studies have shown that black women tend to have higher bone mineral density reserve compared to Caucasians. To the best of our knowledge no study has described the effect of AIs on bone mineral density in black African women. The aim of this study was therefore to assess whether there is a difference in effect of aromatase inhibitors on bone mineral density in black African women with breast cancer.

Objective: To determine the change in bone mineral density in black African breast cancer patients before and after initiation of aromatase inhibitors. Methods: This was a retrospective cohort study between January 2012 and December 2021. All black African women with breast cancer who were on aromatase inhibitors and have had dual energy x-ray absorptiometry (DXA) scans performed at baseline before initiation of AIs and follow up DXA scans 1-2 years later were included in the study. The change in bone density was evaluated comparing the two scans. A control group of black African women of similar age group but with no risk factors for secondary osteoporosis undergoing routine DXA scan was evaluated; this was then matched for age and the level of bone density was compared between the two groups. Prevalence of osteoporosis for black African women was established from the control group.

Data analysis: A paired t-test was used to evaluate the change in BMD between the baseline and follow-up DXA scans. Chi square test was used to assess the difference in BMD between the cases and the control.

Results: The site based paired difference BMD reduction between the baseline and follow-up was 0.01 g/cm2 for lumbar spine (1.1% reduction), 0.02 g/cm2 for proximal femur (1.1% reduction) and 0.01 g/cm2 for neck of femur (1.3% reduction) over an average period of 1.6 years. Comparing the cases at follow-up DXA scan and the control groups the BMD was lower in cases which was 0.81 g/cm2 compared to controls which was 0.86 g/cm2. The prevalence of osteopenia and osteoporosis in black African women was 59% and 10% respectively.

Conclusion: The extent of BMD reduction in this study for black African women with breast cancer on AIs was 1.1% in both lumbar spine and proximal femur and 1.3% in the neck of the femur which was lower compared to the Caucasian population. This corroborates with the available data that black women have higher bone mineral density at all sites measured compared to white women. The prevalence of osteopenia and osteoporosis in black African women in this study was 59% and 10% respectively

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