Study Looks for Link Between Oncotype DX Test Use and Chemotherapy in Older Diagnosed Women

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The Oncotype DX test is a genomic test that analyzes the activity of a group of 21 genes that can affect how a cancer is likely to behave and respond to treatment.

Doctors use the Oncotype DX test to help figure out a woman’s risk of early-stage, estrogen-receptor-positive breast cancer coming back (recurrence), as well as how likely she is to benefit from chemotherapy after breast cancer surgery.

A second test, the Oncotype DX DCIS test, analyzes 12 genes and helps doctors figure out a woman’s risk of DCIS coming back and/or the risk of a new invasive cancer developing in the same breast, as well as how likely she is to benefit from radiation therapy after DCIS surgery.

The Oncotype DX test results assign a Recurrence Score -- a number between 0 and 100 -- to the early-stage breast cancer. You and your doctor can use the following ranges to interpret your results for early-stage invasive cancer:

  • Recurrence Score lower than 18: The cancer has a low risk of recurrence. The benefit of chemotherapy is likely to be small and will not outweigh the risks of side effects.
  • Recurrence Score of 18 up to and including 30: The cancer has an intermediate risk of recurrence. It’s unclear whether the benefits of chemotherapy outweigh the risks of side effects.
  • Recurrence Score greater than or equal to 31: The cancer has a high risk of recurrence, and the benefits of chemotherapy are likely to be greater than the risks of side effects.

A study has found that older women diagnosed with early-stage, estrogen-receptor-positive disease who had the Oncotype DX test were no more or less likely to have chemotherapy after surgery than women who didn’t have the test.

The study was published online on Aug. 27, 2015 by the journal JAMA Oncology. Read the abstract of “Association Between Use of the 21-Gene Recurrence Score Assay and Receipt of Chemotherapy Among Medicare Beneficiaries With Early-Stage Breast Cancer, 2005-2009.”

Earlier studies have found that about 20% to 30% of doctors said they changed their recommendation about chemotherapy based on Oncotype DX test score results. But according to the researchers who did this study, none of the previous studies looked at how having the Oncotype DX test affected whether a woman would have chemotherapy in a real-world clinical setting. So they decided to investigate.

To do the study, the researchers looked at information in the SEER database on women covered by Medicare who were diagnosed with early-stage, estrogen-receptor-positive breast cancer and had the Oncotype DX test between 2005 and 2009. SEER databases are large registries of cancer cases from sources throughout the United States maintained by the National Institutes of Health.

Women covered by Medicare must be 65 or older, so all the women in the study were 65 or older.

National Comprehensive Cancer Network (NCCN) guidelines classified the breast cancer of the 44,044 women in the study as:

  • 24.0% had low-risk disease
  • 51.3% had intermediate-risk disease
  • 24.6% had high-risk disease because of lymph node involvement

The NCCN is an alliance of the world's leading cancer centers. These NCCN centers collaborate on research, guidelines, and education to improve the care of people diagnosed with cancer.

Overall, 14.3% of the women were treated with chemotherapy within a year of their diagnosis.

The researchers found that having the Oncotype DX test had no effect on whether the women had chemotherapy after breast cancer surgery. Women who were tested were no more or no less likely to get chemotherapy than women who weren’t tested.

When the researchers looked at each NCCN classification group, they found some differences in the relationship between getting the Oncotype DX test and the likelihood of getting chemotherapy. Women diagnosed with NCCN-classified high-risk disease were less likely to get chemotherapy if they had an Oncotype DX test, especially women ages 66 to 70. Women with NCCN-classified low-risk disease were more likely to get chemotherapy if they had an Oncotype DX test.

The researchers did not have access to the Oncotype DX test results for the women, so they couldn’t tell if the NCCN classifications coincided with the Recurrence Score estimated risk of recurrence.

“This limitation of the study affected the extent to which we could determine how the [Recurrence Score] results were being used to guide chemotherapy within individual patients, and remains an area of ongoing research,” said Michaela Dinan, Ph.D. of the Duke Cancer Institute and the Duke Clinical Research Institute and lead author of the study.

So it’s possible that some women with NCCN-classified high-risk disease because of lymph node involvement had an Oncotype DX Recurrence Score of lower than 18, which would have put them in the low risk of recurrence category, and may have meant that they opted not to have chemotherapy. And some women with NCCN-classified low-risk disease might have had a Recurrence Score higher than 31, which would put them in the high risk of recurrence category, so they may have decided to have chemotherapy.

Another limitation of the study was that women younger than 65 weren’t included; most women diagnosed with breast cancer are younger than 65. Earlier studies on the Oncotype DX test included a wider range of ages. In those studies 40% to 50% of the women were treated with chemotherapy, compared to only 14.3% in this study.

The relatively small number of women who received chemotherapy in this study could be because of the women’s age. Older women are more likely to have other health conditions that may prevent them from getting chemotherapy. Doctors also may not want to prescribe chemotherapy for certain older women if they feel the side effects will be too debilitating.

Finally, we don’t know anything else about the women’s health and why their doctors would or would not recommend chemotherapy. The Oncotype DX Recurrence Score is just one factor that helps make treatment decisions.

If you’ve been diagnosed with early-stage, estrogen-receptor-positive breast cancer and are weighing the pros and cons of adding chemotherapy to your treatment plan, the Oncotype DX test may help you and your doctor make that decision. Besides any genomic test results, you and your doctor will consider other factors when developing your treatment plan, including:

  • your age
  • the size of the cancer
  • hormone-receptor protein levels
  • the grade of the cancer
  • any other health conditions you have
  • your personal preferences

Together, you can make the best treatment decisions for YOU!

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