21-Gene Assay Score and Chemotherapy Decision-Making in Node-Positive Early Breast Cancer

Key Points

  • Prior to trial results being published, oncologists are already adopting the inclusion criteria of the ongoing RxPONDER trial, which looks at low to intermediate recurrence scores and compares patients treated with hormone therapy alone to those treated with hormone therapy in combination with chemotherapy.
  • Use of the recurrence score assay is an independent predictor of a lower likelihood of chemotherapy being recommended in node-positive early breast cancer. This suggests that oncologists are using the RxPONDER cutoff when making recommendations for patients, despite a lack of evidence.
  • These findings also suggest that doctors are treating patients according to tumor biology, rather than tumor size or stage.

The 21-gene recurrence score assay, Oncotype DX, determines a score that estimates the likelihood of distant recurrence of disease in women with early-stage estrogen receptor–positive breast cancer; this score is used to assess the benefit of adjuvant chemotherapy. Testing with this assay is not recommended for women with intermediate- or high-risk, node-positive breast cancer because significant evidence exists that patients in this population benefit from adjuvant chemotherapy. That said, a recent study conducted by the University of Colorado Cancer Center found that oncologists are indeed using the 21-gene recurrence score assay in patients with high-risk disease and, in some cases, forgoing adjuvant chemotherapy as a result. The study was published by Jasem et al in the Journal of the National Comprehensive Cancer Network.

“To our knowledge, this is the largest study that deals with the current trends of  [21-gene recurrence score] assay use in the node-positive breast cancer population in the United States,” said first author Jagar Jasem, MD, hospitalist at the University of Colorado.

For this study, researchers used the National Cancer Database to evaluate more than 80,000 node-positive early breast cancer cases diagnosed between 2010 and 2012.

Study Findings

The study indicates that, prior to trial results being published, oncologists are already adopting the inclusion criteria of the ongoing RxPONDER (Rx for Positive Node, Endocrine Responsive Breast Cancer) trial, which looks at low to intermediate recurrence scores and compares patients treated with hormone therapy alone to those treated with hormone therapy in combination with chemotherapy.

“The adoption of new modalities while prospective studies are ongoing is not new for the oncology field, with mixed results. For many years, use of high-dose chemotherapy intensification followed by autologous bone marrow or stem cell rescue was used and adopted as a standard of care before the completion of prospective randomized trials that were ultimately negative,” said Peter Kabos, MD, Assistant Professor of Medical Oncology at the University of Colorado.

The University of Colorado researchers found that the recurrence score assay is an independent predictor of a lower likelihood of chemotherapy being recommended in node-positive early breast cancer. This suggests that oncologists are using the RxPONDER cutoff when making recommendations for patients, despite a lack of evidence. It also suggests that doctors are treating patients according to tumor biology, rather than tumor size or stage.

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) for Breast Cancer—the recognized standard of cancer care in the United States—recommend adjuvant chemotherapy in patients with node-positive breast cancer.

Additional Data

In breaking down the data, researchers noticed trends showing that race, treatment setting, and insurance coverage influenced whether patients received 21-gene recurrence score testing and whether they were treated with chemotherapy.

Black women with breast cancer have higher mortality rates and higher-risk cancers, including triple-negative breast cancer, compared with other patient populations. Nevertheless, Dr. Jasem’s study revealed that black women were significantly less likely to receive 21-gene recurrence score testing compared with women of other races.

“Black women may be less likely to get tested because oncologists tend to treat them with chemotherapy, regardless of the test result,” the authors noted. “Our study, similar to others, documented a higher-risk disease in this patient population, which together with patient preference may play a role in final decision-making. However, there are no data currently available that suggest differential use of the test or chemotherapy based on racial factors alone.”

When observing site of care, the researchers found that, compared with patients treated at community centers, patients at academic or comprehensive cancer centers were more likely to receive 21-gene recurrence score assay testing, but no discrepancies were noted regarding chemotherapy recommendations among all patients tested.

As a key indicator of socioeconomic status, insurance coverage played a major role in recurrence score assay testing recommendations. The study showed that insured patients were more likely to have the recurrence score test compared to uninsured patients, and the privately insured were more likely to have it than the governmentally insured. Furthermore, in the absence of testing, insured patients were significantly more likely to be recommended chemotherapy than uninsured patients.

“The results of well-designed clinical trials often inform clinical practice. As pointed out by Jasem and colleagues, clinicians not infrequently follow their instincts, rather than wait for the data from a trial. This practice may have unintended consequences, including recommending adjuvant chemotherapy, or not, inappropriately—denying benefit to some and exposing unnecessary toxicity to others,” said William J. Gradishar, MD, of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University and Chair of the NCCN Guidelines® panel for breast cancer.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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