Researchers recently explored whether the genetic landscape of tumours could be captured through blood collection in African women with breast cancer.
By 2040, cancer mortality is expected to increase by more than 92% in Africa. This is the highest prediction out of all the continents. Moreover, it is expected there will be more deaths caused by non-communicable diseases, such as cancer, than infectious diseases in Africa by 2030.
It is clear that cancer creates a huge clinical, economic and social burden for the continent. Therefore, it is unfortunate that individuals of African origin make up less than 3% of study participants in genome-wide association studies (GWAS). This translates to a limited representation of African populations in cancer genomics research. This is particularly alarming because Africa has the most diverse population on the planet and accounts for 17% of the global human population.
Studying breast cancer in Ghana
Breast cancer in Africa has a high mortality rate and is fast becoming the most common cancer in the continent. In fact, in Ghana over 60% of breast cancer patients are diagnosed late with tumours larger than 5cm in size. This is mostly due to the lack of mammography screening programmes. Notably, around 64% of breast cancer cases in Ghana are in women below the age of 55.
Recently, a group of scientists worked with the Ghana Breast Health Study team to test if circulating tumour DNA (ctDNA) technologies could be used to investigate the molecular pathology of cancer in understudied populations, such as those in Ghana. ctDNA is found in the bloodstream. Techniques for detecting ctDNA to characterise and monitor cancer have matured rapidly over the years. However, these methods have mostly been studied in European populations.
The aim of this study was to determine whether the genetic landscape of tumours could be captured through blood collection and whether ctDNA would be readily detectable in Ghanaian women with breast cancer.
Fifteen patient plasma samples were collected at the time of diagnosis and analysed. Whole-genome sequencing at high and low depths revealed that ctDNA and breast cancer copy number alternations were identified in the majority of patients. This suggests that whole-genome sequencing, even at low depths, could reveal somatic alterations linked to breast cancer in African women. This finding is exciting as the detection of ctDNA in plasma samples could be both clinically relevant and feasible within Ghanaian clinics.
The future of African cancer genomics
Overall, this study has provided evidence for the fact that genomic information can be obtained by sequencing ctDNA from plasma samples of breast cancer patients in Ghana. Moving forward, technologies for detecting ctDNA could be used to further understand the molecular pathology of cancer in understudied populations and act as a means to improve early diagnoses in low-income regions. Although delays to cancer diagnosis in Africa is a multifaceted challenge that requires improved education programmes and outreach services, increasing access to available treatments early on could significantly improve survival outcomes.
Increasing ethnic diversity in genomic research is paramount, particularly in African populations where more aggressive early-onset breast cancers are prevalent. Improved points of care that use non-invasive molecular diagnostics, such as ctDNA studies, may provide novel insights for cancer treatment and assist in diagnosing patients quicker. This will seem increasingly feasible as sequencing technologies become more affordable.
Nevertheless, continued research is needed to explore the clinical utility of ctDNA in Ghanaian populations. These studies could have an increased target sequencing coverage and depth to reliably determine clinically relevant somatic mutations. This could be done by incorporating whole-exome sequencing or high-coverage gene panels.
Furthermore, exploring larger datasets and sequencing results from other populations will enable scientists to determine why the African cancer incidence is rising. Could it be purely due to ancestry, or perhaps a different molecular effect? Future research will be crucial for answering these questions and promoting precision medicine in different global populations, such as in African-clinical settings.
Image credit: Moffitt Cancer Center
