Breast cancer screening, such as mammography, is important for determining a woman's risk for the disease, but such screening can sometimes produce inconsistent results. Now, a new study claims genomic sequencing could be useful for identifying women who are most likely to benefit from screening, and it could also offer women a chance to reduce their risk of breast cancer.
The research team, including Prof. Alice Whittemore of the Department of Health Research and Policy at Stanford Cancer Institute in California, publish their findings in the journal Cancer Epidemiology, Biomarkers & Prevention.
Breast cancer is the second leading cause of death among American women, behind lung cancer. This year, it is expected that around 232,670 women will be diagnosed with invasive breast cancer and 40,000 will die from the disease.
Since 1989, however, death rates from breast cancer have been declining. According to the American Cancer Society, this is partly down to earlier detection through screening, which leads to earlier treatment.
Mammography is the most common breast cancer screening method, in which an X-ray of the breast is taken to check for tumors that may be too small to detect through a clinical breast exam. The test may also detect abnormal cells that pose a risk for invasive breast cancer.
But such screening methods are not without their risks. A mammography, for example, can show false-negative results, meaning a woman who has breast cancer may fail to undergo treatment because her results appear normal. On the other hand, screening may produce false-positive results, meaning a woman may be subject to further examination or treatment for no reason.
"We need low-cost screening tools that can discriminate between women who will and won't develop fatal breast cancer that are more effective than those currently available," says Prof. Whittemore.
Genomic sequencing 'more effective for disease prevention than previously thought'
As such, the team looked to genomic sequencing - a process in which specific genes linked to certain diseases can be identified through searching small sections of DNA.
- A woman's lifetime risk of dying from breast cancer is around 1 in 36
- Breast cancer risk increases with age; 2 out of 3 invasive breast cancers are found in women aged 55 and over
- There are more than 2.8 million breast cancer survivors in the US.
Prof. Whittemore notes that past research claims sequencing the genomes of women, ranking genes by risk and targeting genes that present high risk will not be an effective breast cancer prevention technique. But this latest study challenges these claims.
After analyzing previously published data on 86 breast cancer gene variants known to be linked to breast cancer risk, the team created a computational model to estimate a woman's lifetime risk of developing breast cancer.
Prof. Whittemore explains that this was done by calculating a risk score, which is the number of breast cancer-related genetic variants a woman has multiplied by the effects of these variants.
The team found that based on the 86 breast cancer gene variants, the lifetime risk for the entire female population stood at 0.35, significantly higher than the 0.07 variance the researchers say was identified in a previous study.
The researchers believe these findings indicate that genomic sequencing has the potential to effectively predict a woman's risk of breast cancer.
"Our estimates suggest that preventive strategies based on genome sequencing will bring greater gains in disease prevention than previously projected," says Prof. Whittemore. "Moreover, these gains will increase with increased understanding of the genetic etiology of breast cancer."
Commenting on their findings, first author Dr. Weiva Sieh, assistant professor and epidemiologist at Stanford Cancer Institute, says:
"As we keep identifying additional breast cancer variants that can further explain the difference between my risk versus yours, the variance of the genetic risk score in the population will increase, and the potential utility of genomic sequencing will grow.
Our ability to predict the probability of disease based on genetics is the starting point. If a girl knew, from birth, what her inborn risk was, she could then make more informed choices to alter her future risk by altering her modifiable factors, such as diet and lifestyle."
Medical News Today recently reported on a study claiming breast cancer screening for women over the age of 70 could lead to overdiagnosis.