Inherited Cancer and Non-Inherited Cancer: What’s The Difference?
Note: This post is written by Susanne Haga, Education Director of the Duke Center for Genomic and Computational Biology and the Duke Center for Applied Genomics and Precision Medicine. She is an Associate Professor of Medicine at Duke University School of Medicine. Part of her work focuses on how to effectively communicate genomic test results to patients, assisting patients with understanding the impact of the test result for their health, and helping health providers obtain the knowledge resources they need to appropriately deliver genomic medicine. Dr. Haga’s work has resulted in numerous publications in leading journals and books.
Many of us have likely heard that October is Breast Cancer Awareness Month. However, the urgency of breast cancer advocacy doesn’t end November 1st. Underscoring this fact is a sobering statistic: In 2017 alone, an estimated 252,710 new cases of invasive breast cancer will be diagnosed among women.1
Many of us have a basic understanding of how cancer grows in the body as a result of changes in DNA (genes). Yet, though all cancer is genetic, not all cancers are inherited. I know this distinction may seem confusing, so bear with me as I try to explain. Cancer develops because the DNA in some cells becomes damaged. “Mutation” in fact refers to this damage, which is essentially a change in the DNA code. The DNA code acts as an instruction manual for cells, sort of like a computer code, so if the code is messed up, the instructions may be messed up too, causing the cells to behave abnormally.
Mutations that can lead to various cancers accumulate throughout our lifetime due to a variety of factors, including sun exposure (that’s why sunscreen is important!), obesity, some viral infections (linked to cervical cancer), and/or random mistakes that occur in the DNA when cells grow. These accumulations help explain why the risk for breast cancer increases with age: at age 30, 1 in 227 women will develop breast cancer, but at age 70, 1 in 26 women will develop breast cancer.2 Ultimately, many cancers are not inherited, because a mutation in a cancer-related gene has not been passed on from one of the parents. However, heredity remains a factor in numerous other instances of cancer, and can be a life-saving tool for identifying other at-risk family members.
Increasing visibility of those affected by inherited cancer are personalities like actresses Angelina Jolie and Christina Applegate, who have both disclosed a history of breast and/or ovarian cancer in their family. Both women tested positive for a genetic mutation linked to breast/ovarian cancer that is often found in families like theirs. This inherited mutated gene, known as BRCA, significantly raises cancer risk–though it doesn’t mean a person will definitely develop cancer. Ultimately, cancer is rarely due to a single mutation. It more often results from many mutations that have accumulated over many years. And individuals with an inherited cancer gene have an even greater susceptibility to developing cancer than the rest of us.
Ms. Jolie underwent surgery to prevent breast and ovarian cancer. Ms. Applegate was diagnosed with breast cancer and later had her ovaries removed to reduce risk of ovarian cancer. These prophylactic surgeries, an option considered based on their genetic test results and family history, allowed both women to deny cancer its claim to their bodies. But prophylactic surgery is often a more extreme measure, and other options may be considered by women in these circumstances. It is essential to discuss the options with your healthcare providers and family. Genetic testing is key to understanding your risks and the range of options available to you, as it empowers you to become more informed, involved, and proactive with regard to your health.