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Adding Genetic Information to Breast Cancer Risk Prediction Tool Doesn’t Improve Accuracy

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A study suggests that adding information on about 10 abnormal genes associated with breast cancer risk to the standard breast cancer risk assessment tool didn't really improve risk prediction compared to using only the standard tool.

There are links between abnormal genes and many diseases, including several types of cancer. By analyzing whether someone has these abnormal genes, researchers hope to pinpoint a person's risk for specific diseases, including breast cancer.

In many cases, researchers are still working on making this genetic-based risk assessment a reality. One success story is testing for the abnormal breast cancer genes BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two) in women at high risk based on personal and family medical history. Most inherited cases of breast cancer are associated with one of these two abnormal genes. Women with an abnormal BRCA1 or BRCA2 gene have up to an 85% risk of developing breast cancer by age 70. Their risk of ovarian cancer also is higher than average. Men with an abnormal BRCA1 or BRCA2 gene have a higher risk of both breast and prostate cancer.

This study compared risk assessments of 5,590 women diagnosed with breast cancer to risk assessments of 5,998 similar women without breast cancer. The researchers compared three risk assessment tools to see if one was more accurate than the others:

  • Gail score: The Gail score, the standard breast cancer risk assessment tool, assesses breast cancer risk based on a series of personal health questions that women and their doctors answer together. The questions ask about risk factors such as age, child-bearing history, family history of breast cancer, and breast biopsy results. The Gail score estimates the risk of developing invasive breast cancer in the next 5 years.
  • Gene analysis: This gene analysis looked at 10 abnormal genes (called single nucleotide polymorphisms or SNPs) associated with breast cancer risk.
  • Adding gene analysis to the Gail score.

The researchers used very complicated math formulas to analyze the results. They found that adding gene analysis to the Gail score improved breast cancer risk prediction only a little compared to the risk predicted by just the Gail score.

While these results don't seem very promising, there are reasons to be hopeful. More than 1,000 abnormal genes may be linked to breast cancer risk. For genetic testing to dramatically improve risk prediction, the tests would need to include many more than the 10 abnormal genes studied here. But because the 10 abnormal genes the researchers analyzed did improve breast cancer risk prediction slightly, there's hope that a test that analyzes more genes may be a useful tool to more accurately determine breast cancer risk. Much more research is needed.

If you're wondering what your risk of breast cancer is, you might want to talk to your doctor about your personal and family medical history. You and your doctor also may want to calculate your Gail score and talk about what it means. The National Cancer Institute web site has more information about the Gail score.

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