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Tumor gene test may determine which breast cancer patients can forgo chemotherapy


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Because women may experience negative side effects after chemotherapy, researchers wanted a way to determine which breast cancer patients can avoid chemotherapy without affecting their survival. This study suggests that a test that looks at 70 genes in breast tumors may be able to identify breast cancer patients who can do without chemotherapy for their disease. (9/13/16)


STUDY AT A GLANCE

This study is about:

Whether MammaPrint, a test that looks at 70 genes in breast cancer tumors, can reliably determine which patients should get chemotherapy, focusing on women who were determined to be at high risk for breast cancer recurrence using a program that takes into account many clinical factors.

Why is this study important?

The study authors write, “A substantial number of patients with breast cancer are over treated and are thus being exposed to the risk of toxic effects from adjuvant therapy without deriving significant benefit.” This gene test may help healthcare providers determine which women can receive no chemotherapy, and avoid being over treated.

Study findings: 

  1. The five-year metastasis free survival rate of women who were considered at high clinical risk of recurrence based on personal and tumor characteristics and whose tumors received a low score on the 70-gene signature MammaPrint test (meaning they had low genomic risk of breast cancer) and did receive chemotherapy was 95%.
    • The five-year metastasis free survival rate of these women who did NOT receive chemotherapy was 96%.

What does this mean for me?

Women at high clinical risk for breast cancer recurrence may be advised to get chemotherapy, but these results suggest that of these women, those who receive a low score on the 70-gene signature MammaPrint test may not need to get chemotherapy. More work needs to be done to study longer-term outcome (for example, 10-year survival rates and longer). Ultimately, breast cancer patients should ask their healthcare providers if they have more questions about the 70-gene signature MammaPrint test and work together to determine the treatment options that are best for them.

Questions to ask your health care provider:                                           

  • How does MammaPrint work?
  • Can I safely avoid chemotherapy if MammaPrint says I am at low genomic risk?
  • Can you help me determine what my risks and benefits are if I receive chemotherapy?
  • Are there other tests that can be used to determine whether or not I will benefit from chemotherapy?

IN DEPTH REVIEW OF RESEARCH

Study background:

Early stage breast cancer patients are usually treated with chemotherapy, endocrine therapy, drugs against human epidermal growth factor receptor 2 (HER2), or a combination of these three. Some of these patients may be over treated, meaning they are getting some treatments they don’t need. These treatments can have negative side effects and expose patients to the risk of side effects caused by the treatments’ toxicity. 

As a result, Fatima Cardoso and her colleagues at the Champalimaud Clinical Center and other institutions published work in The New England Journal of Medicine in August 2016 that assessed whether a 70-gene signature test on breast cancer tumors could determine which women could avoid chemotherapy. The researchers especially wanted to look at the group of women who were at high clinical risk (determined using Adjuvant! Online, a program that provides information on a woman’s 10-year probability of breast cancer survival with a specific treatment or no treatment based on factors including age, menopausal status, ER status of the tumor, and the number of lymph nodes involved) and had a low score on their 70-gene signature test, which they considered as being at “low genomic risk.”

Researchers of this study wanted to know:

Could early stage breast cancer patients who are at high clinical risk (meaning they have a low probability of 10-year survival without treatment) but are at low genomic risk according to MammaPrint safely avoid chemotherapy?

Population(s) looked at in the study:

The 6,693 women involved in this study were between 18 and 70 years old and had primary invasive breast cancer. Women were allowed to participate in the study if they had a maximum of three positive lymph node invasions in their underarm area. The researchers used two different tests to group the patients:

  • The Adjuvant! Online program was used to determine clinical risk. Using this test, patients were classified as “high clinical risk” or “low clinical risk” based on age, menopausal status, ER status of the tumor, and the number of lymph nodes involved.
  • The MammaPrint 70-gene signature test was used to determine genomic risk, with a low MammaPrint score defined as low genomic risk and a high score defined as high genomic risk

Using these tests, the women were placed into one of four groups:

  1. High clinical risk/high genomic risk
  2. High clinical risk/low genomic risk
  3. Low clinical risk/high genomic risk
  4. Low clinical risk/low genomic risk.

The women who were in the low clinical risk/high genomic risk and high clinical risk/low genomic risk were randomized to determine who would receive chemotherapy.

Study findings: 

  1. The five-year metastasis free survival rate of women who were considered at high clinical risk of recurrence based on personal and tumor characteristics and whose tumors received a low score on the 70-gene signature MammaPrint test (meaning they had low genomic risk of breast cancer) and did receive chemotherapy was 95%.
    • The five-year metastasis free survival rate of these women who did NOT receive chemotherapy was 96%.

Limitations:

The researchers cannot tell if the difference in survival rates between the high clinical risk and low score on MammaPrint women who did receive chemotherapy and the women who did not is significant. However, as stated by Clifford Hudis and Maura Dickler in their accompanying commentary on this research study, if the difference is real, it “might mean more to one patient than to another.”

Additionally, this study did not specifically look at women who are at increased risk for breast cancer, including women with mutations in cancer risk increasing genes (for example, BRCA). Therefore, it is not known if these findings would be the same for women with such mutations.  

Conclusions:

Using tumor genetic tests to help make treatment decisions currently is an active area of research.  The Oncotype DX test is one such 21-gene test that can help patients and their healthcare providers make treatment decisions. National guidelines, including NCCN, suggest that healthcare providers  consider using this 21-gene test to quantify breast cancer recurrence risk and predict how ER+ and HER2- patients will respond to tamoxifen and chemotherapy.

The current study of the MammaPrint 70-gene test differs from previous work on the 21-gene  Oncotype DX test because that study focused on women considered to be at high clinical risk of recurrence based on standard personal and tumor characteristics. This work examined whether or not a subset of these patients could be identified who could avoid chemotherapy based on the results of the 70-gene MammaPrint test.  The results of this study suggest that patients at high clinical risk of breast cancer who scored low on the MammaPrint 70-gene signature test and didn’t receive chemotherapy had similar five-year survival rates to women who did receive chemotherapy. But as the study authors write, “ultimately, the decision to receive or forgo chemotherapy (or any other treatment) lies with each patient who is properly informed about the potential side effects and the potential benefits of such treatment. For the same risk-benefit scenario, different patients may make different decisions.” Hudis and Dickler echo the same sentiment in their editorial, writing, “In the clinic today, these results could allow some doctors and patients to choose to avoid chemotherapy if they have carefully considered their own tolerance for toxicity, risk, and uncertainty.” When making treatment decisions, therefore, patients need to discuss with their healthcare provider those factors that are most important to them.

Posted 9/13/16

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References

Cardoso F, van’t Veer LJ, Bogaerts J, et al. “70-gene Signature as an Aid to Treatment Decisions in Early-Stage Breast Cancer.The New England Journal of Medicine. 2016; 375 (8): 717-729.   

Hudis CA, Dickler M. “Increasing Precision in Adjuvant Therapy for Breast Cancer.The New England Journal of Medicine. 2016; 375 (8): 790-791.  

NCCN Clinical Practice Guidelines in Oncology:  Breast Cancer Version 2.2106, May 5, 2016.  

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