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21-Gene Assay - Are Oncologists Jumping the Gun?

  • Published: 2017-04-17 : Author: National Comprehensive Cancer Network : Contact:
  • Synopsis: Study uncovers discrepant decision making for use of 21-gene assay in women with cancer.
21 Gene Signature

A test that is used to help predict whether breast cancer will spread to other parts of the body or come back. The test looks at the activity of 21 different genes in breast cancer tissue of women who have early-stage breast cancer that is estrogen receptor positive and has not spread to the lymph nodes. If there is a high risk that the cancer will spread or come back, it may be used to help plan treatment with anticancer drugs. Also called Oncotype DX breast cancer assay.

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"To our knowledge, this is the largest study that deals with the current trends of the RS assay use in the node-positive breast cancer population in the United States, said Dr. Jasem."

University of Colorado Cancer Center Study uncovers discrepant decision-making for use of 21-gene assay in women with cancer: testing occurs in high-risk population, despite current evidence; non-concordance with NCCN Guidelines® recommendations; and racial and socio-economic disparities found in testing use.

The 21-gene recurrence score (RS) assay, Oncotype DX™ (ODx), determines a score that estimates the likelihood of distant recurrence of disease in women with early-stage estrogen receptor-positive (ER+) breast cancer; this score is used to assess the benefit of adjuvant chemotherapy. RS testing is not recommended for women with intermediate- or high-risk, node-positive breast cancer because significant evidence exists that patients in that population benefit from adjuvant chemotherapy. That said, a recent study out of the University of Colorado Cancer Center finds that oncologists are indeed using the RS assay in patients with high-risk disease and, in some cases, foregoing adjuvant chemotherapy as a result.

The study, "The 21-Gene Recurrence Score (RS) Assay for Node-Positive Early Breast Cancer and Impact of RxPONDER Trial on Chemotherapy Decision-Making," led by Jagar Jasem, MD, MPH, and Peter Kabos, MD, was published in the April issue of JNCCN -- Journal of the National Comprehensive Center Network.

"To our knowledge, this is the largest study that deals with the current trends of the RS assay use in the node-positive breast cancer population in the United States," said Dr. Jasem.

For this study, Jasem et al used the National Cancer Data Base (NCDB) to evaluate more than 80,000 node-positive early breast cancer cases diagnosed between 2010 and 2012.

Ongoing Study and Current Recommendations

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 RS 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 Dr. Kabos.

The University of Colorado researchers found that RS assay is an independent predictor of less chemotherapy recommendation in node-positive early breast cancer. This suggests that oncologists are using the RxPONDER cut-off 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.

Who, Where, and Why?

In breaking down the data, researchers noticed trends showing that race, treatment setting, and insurance coverage influenced whether or not patients received ODx 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. Despite that, Dr. Jasem's study revealed that black women were significantly less likely to receive RS testing compared with women of other races. [Gross, et al, reported similar results in the March issue of JNCCN:]

"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 RS 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 RS assay testing recommendations. The study showed that insured patients were more likely to have the RS test compared to uninsured patients, and the privately insured more than the governmentally insured. Furthermore, in the absence of testing, insured patients were significantly more likely to be recommended chemotherapy than uninsured.

"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, Robert H. Lurie Comprehensive Cancer Center of Northwestern University; Chair of the NCCN Guidelines® panel for Breast Cancer,

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