--- title: Breast Cancer and Chemotherapy: Genetic Test Guides Decisions description: A study investigates for the first time how a gene-based test is affecting women’s decisions to get chemotherapy after a breast cancer diagnosis canonical: https://time.com/4013180/genetic-test-impact-chemo-choices-in-surprising-ways/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2015-08-27T15:00:28.000Z article:modified_time: 2026-02-22T10:29:42.092Z article:section: Health og:title: Genetic Test Impact Chemo Choices In Surprising Ways og:description: A study investigates for the first time how a gene-based test is affecting women’s decisions to get chemotherapy after a breast cancer diagnosis og:url: https://time.com/4013180/genetic-test-impact-chemo-choices-in-surprising-ways/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltfcdfad9583867d5c/6988612e524fc0e276df4421/gettyimages-568857577.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 5000 og:image:height: 2813 og:image:alt: 568857577 og:type: article twitter:card: summary_large_image twitter:title: Genetic Test Impact Chemo Choices In Surprising Ways twitter:description: A study investigates for the first time how a gene-based test is affecting women’s decisions to get chemotherapy after a breast cancer diagnosis twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltfcdfad9583867d5c/6988612e524fc0e276df4421/gettyimages-568857577.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Genetic Test Impacts Chemo Choices In Surprising Ways > Sponsored content. 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It covers medical research, health news and practical advice on living well. #### Where can I get reliable health news by email? Health Matters is TIME's weekday health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free weekday newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ### Sources * TIME Newsletters: [time.com/newsletters](/c/time-nl-health-2026q3/newsletters?i=e8030b9c-4759-4f7e-9a67-efa8702e73c6&cr=time-nl-health-2026q3-v1)  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Aug 27, 2015 3:00 PM UTC  Computer representation of DNA chain Computer representation of DNA chain Maciej Frolow—Getty Images  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Aug 27, 2015 3:00 PM UTC Correction appended, Aug. 31, 2015 In the new era of personalized medicine, having more information on hand is considered the ideal situation for making more customized, and ideally, effective decisions about medical care. And in a new study of breast cancer patients, researchers show that a relatively new genetic test for evaluating tumors is doing just that. It’s just that the test isn’t necessarily leading to the decisions that experts expected. The Oncotype DX Breast Cancer Assay is a [test launched in 2004 ](http://content.time.com/time/specials/packages/article/0,28804,1852976%5F1852971%5F1852952,00.html) to help women decide how likely their breast cancer is to recur. The score, from zero to 100, is for women with breast tumors that have not spread to the lymph nodes. It places women on a scale of probability, based on an analysis of 21 genes in her tumor. Most doctors and patients use the score to decide, in part, whether the woman should receive chemotherapy following surgery. **MORE:** [A Major Shift in Breast Cancer Understanding](http://time.com/4004767/dcis-breast-cancer-treatment/) In previous studies, about 20% to 30% of doctors say they changed their recommendation about chemotherapy based on the Oncotype DX score. But none of the studies looked at how Oncotype DX affected the likelihood a woman would undergo chemotherapy rates in a real-world setting— outside of a trial. In clinics, says Michaela Dinan, assistant professor in medical oncology at the Duke Cancer Institute, many other factors contribute to treatment decisions, including fear, family history and physician advice. So she and her colleagues conducted a review of data on more than 44,044 breast cancer patients to see how the Oncotype test affected chemotherapy decisions. **MORE:** [Here’s the Amount of Exercise That Lowers Breast Cancer Risk](http://time.com/3960035/exercise-breast-cancer/) The results, [published in _JAMA Oncology_](http://www.elabs10.com/c.html?ufl=c&rtr=on&s=x8pbgr,2boph,2kek,dz0m,4cpg,hb35,8zrx), showed that overall, the test had no effect on their decision. Women who were tested were no more or no less likely to opt for chemotherapy than those not getting Oncotype DX. Younger age and a higher risk disease were more likely to predict chemotherapy use than the assay. While many assumed that the test would lead to fewer treatments, Dinan’s data shows that _how_ the testing affects chemotherapy decisions is less predictable. When Dinan delved further into the numbers, she found an interesting pattern. Those rated as having high-risk breast cancer according to the National Comprehensive Cancer Network guidelines were less likely to get chemo than women who were not tested. And among people with low-risk disease, those getting the genetic test were more likely to get chemotherapy than low-risk patients who did not. Because the study did not take into consideration what the Oncotype DX scores were, it’s possible, for example, that women considered high risk who received intermediate or low Oncotype DX scores decided not to undergo chemotherapy since the testing showed their response might not be as positive as they might have expected. On the other hand, women who have low risk disease and receive an intermediate test score might decide to undergo chemotherapy since the intermediate risk might represent a slightly higher risk of recurrence than they were anticipating. “It’s a more nuanced finding,” says Dinan. “The Oncotype DX test is impacting the receipt of chemotherapy, but the impact isn’t in one direction or another in terms of whether people are more or less likely to get chemotherapy.” As more options for personalized treatments make their way into the clinic, Dinan says it’s worth remembering that they shouldn’t dictate decisions but inform them. “The nuanced finding of the difference between high risk and low risk patients says to me that whether or not a woman with early stage breast cancer undergoes chemotherapy is going to be affected by a number of different factors, not just this assay. It’s a personalized discussion about the individual patient’s case.” **Correction:** The original version of this story misstated that the Oncotype DX test is FDA approved. 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