Scientists uncover multiple faces of deadly breast cancer
An international team of scientists, including four at Simon Fraser University, has made a discovery that will change the way the most deadly form of breast cancer is treated.
The journal Nature has just published the team’s findings online in the paper The clonal and mutational evolution spectrum of primary triple negative breast cancers.
The study is the largest genetic analysis of what were thought to be triple negative breast cancer tumours.
The 59 scientists involved in this study expected to see similar gene profiles when they mapped on computer the genomes of 100 tumours.
But to their amazement they found no two genomes were similar, never mind the same. “Seeing these tumours at a molecular level has taught us we’re dealing with a continuum of different types of breast cancer here, not just one,” explains Steven Jones, co-author of this study.
The SFU molecular biology and biochemistry professor, who heads up bioinformatics research at the BC Cancer Agency, adds: “The genetic diversity of these tumours, even though they’re clinically similar, probably explains why they are so difficult to treat. These findings prove the importance of personalizing cancer drug treatment so that it targets the genetic make up of a particular tumour rather than presuming one therapy can treat multiple, similar-looking tumours.”
Breast cancer is the most common cancer diagnosed in the United States, after skin cancer. It is the second leading cause of cancer deaths in women today, after lung cancer. According to the American Cancer Society, more than 230,000 women will be diagnosed with breast cancer annually in the United States, and more than 39,000 will die from the disease.
Breast cancer rates are on the decline, according to the Society. Deaths from breast cancer have decreased by about 2 percent since 1990, likely from earlier detection and advances in treatment.
Incidence By Age
This risk model is based on population averages. Each woman’s breast cancer risk may be higher or lower, depending upon a several factors, including family history, genetics, age of menstruation, and other factors that have not yet been identified.
Incidence By Ethnic Group
All women are at risk for developing breast cancer. The older a woman is, the greater her chances of developing breast cancer. Approximately 77% of breast cancer cases occur in women over 50 years of age.
According to the American Cancer Society, white women develop breast cancer at a higher rate than African-American women, but African-American women are more likely to get breast cancer before they are 40, and are more likely to die from it at any age.
Triple negative breast cancer lacks surface cell receptors for estrogen, progesterone and herceptin - a hormone, steroid and protein, respectively, linked to breast cancer. It strikes 16 per cent of women who develop breast cancer and targets mainly those under age 40.
Scientists consider it the most deadly form of breast cancer because it doesn’t respond well to modern drug therapies, which knock out receptors found in most breast cancers but not this one.
Typically, triple negative breast cancer patients need everything thrown at them - surgery, chemotherapy and radiation - to have any hope of going into remission.
Race/ethnicity and socioeconomic factorsSince 1975, the breast cancer 5-year relative survival rate has increased significantly for both African American and white women; nevertheless there remains a substantial racial gap. In the most recent period, the 5-year relative survival rate was 77% for African American women and 90% among white women.
This survival disparity is attributed to both later stage at detection and poorer stage-specific survival among African American women.
Cause-specific survival rates are used instead of relative survival to describe survival in racial and ethnic minorities because estimates of normal life expectancy are not available for most racial groups. Cause-specific survival is the probability of not dying of breast cancer within 5 years of diagnosis. African American women have the lowest survival rate of any racial or ethnic group, indicating that they have the greatest probability of dying of breast cancer.
Poverty and a lack of health insurance are also associated with lower breast cancer survival.
Breast cancer patients from lowerincome areas have lower 5-year survival rates than those from higher-income areas at every stage of diagnosis.
The presence of additional illnesses, unequal access to medical care, and disparities in treatment likely contribute to differences in breast cancer survival.
Aggressive tumor characteristics associated with poorer prognosis appear to be more common in African American women and may also contribute to lower survival rates.
Jones credits the affordability of genetic sequencing - a process that now takes tens of thousands rather than millions of dollars to do - with making tumour analysis at the molecular level more readily available.
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Other researchers associated with SFU involved in this research are Marco Marra, Martin Hirst and Gregg Morin. As well as being researchers at the Michael Smith Genome Sciences Centre, they are SFU adjunct professors of molecular biology and biochemistry.
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Carol Thorbes
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Simon Fraser University