MammaPrint Test May Help Decide Who Can Skip Chemotherapy

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The MammaPrint test is a genomic test that analyzes the activity of a group of 70 genes from a breast cancer tissue sample that can affect how a cancer is likely to behave and respond to treatment.

In the United States, MammaPrint can be used to analyze early-stage breast cancers that are:

  • stage I or stage II
  • invasive
  • smaller than 5 centimeters

In the rest of the world, MammaPrint can be used on cancers that are:

  • stage I or stage II
  • invasive
  • smaller than 5 centimeters
  • in three or fewer lymph nodes

In both the United States and internationally, MammaPrint can be used to analyze cancers that are hormone-receptor-positive and hormone-receptor-negative.

The MammaPrint test calculates whether the cancer has a low or high risk of coming back (recurring) within 10 years after diagnosis. Knowing if a cancer has a low or high risk of recurrence could help women and their doctors decide if chemotherapy or other treatments are needed after surgery -- called adjuvant treatments -- to reduce recurrence risk.

A study suggests the MammaPrint test can help decide which women can safely skip chemotherapy after surgery.

The research was published in the Aug. 25, 2016 issue of The New England Journal of Medicine. Read the abstract of “70-Gene Signature as an Aid to Treatment Decisions in Early-Stage Breast Cancer.”

There are several other genomic tests used to analyze breast cancer, including the Oncotype DX test. Because the Oncotype DX test has been validated by much research, right now it is the most widely used genomic test for breast cancer. The study summarized here strongly suggests that the MammaPrint test eventually also may be widely used to make decisions about treatments after surgery.

This study was a randomized, prospective study, which means that a large group of people were randomly assigned to one thing or another and then the researchers watched for the outcomes over a long period of time. A prospective study is stronger than a retrospective study, which looks at data collected before the study was designed.

The study included 6,693 women from nine countries diagnosed with early-stage breast cancer who had surgery.

Each woman’s risk of recurrence within 10 years of diagnosis was estimated with two different tests:

  • the MammaPrint test
  • a computer program called Adjuvant! Online that analyzes the clinical characteristics of the cancer, including size, grade, hormone-receptor status, and HER2 status

Women diagnosed with hormone-receptor-positive disease who were estimated to have an 88% or higher chance of being alive 10 years after diagnosis by the computer program, with no chemotherapy or hormonal therapy, were considered “clinical low risk.” Women diagnosed with hormone-receptor-negative disease who were estimated to have a 92% or higher chance of being alive 10 years after diagnosis by the computer program, with no chemotherapy, also were considered “clinical low risk.”

Women considered to have a low risk of recurrence based on BOTH the MammaPrint test and the computer program were not treated with chemotherapy after surgery.

Women considered to have a high risk of recurrence based on the results of both tests were treated with chemotherapy.

Women who had what the researchers called “discordant results” -- meaning one test estimated a high risk of recurrence and the other test estimated a low risk of recurrence -- were treated with radiation therapy after surgery. The researchers then randomly chose one test result to decide if the women would be treated with chemotherapy.

The researchers wanted to see if women who didn’t get chemotherapy because the MammaPrint test estimated low recurrence, even though the computer program estimated high risk, had similar survival rates to women with the same risk estimates who were treated with chemotherapy.

"Our hypothesis was that the MammaPrint genomic assay would outperform the clinical criteria by reducing the prescription of adjuvant chemotherapy without impairing patient outcomes," said Martine Piccart, M.D., of the Jules Bordet Institute in Brussels and lead author of the study. Dr. Piccart also is a member of the Breastcancer.org Professional Advisory Board.

After about 5 years of follow-up, distant metastasis-free survival was:

  • 94.7% for women with estimated high risk by the computer program/low risk by MammaPrint who did not receive chemotherapy
  • 96.2% for women with estimated high risk by the computer program/low risk by MammaPrint who were treated with chemotherapy

Distant metastasis-free survival is living without the cancer coming back in a part of the body away from the breast.

So women who were determined to have a low risk of recurrence by the MammaPrint test had about the same distant recurrence rates, no matter whether they were treated with chemotherapy or not. This suggests the MammaPrint test could be used to help decide which women diagnosed with early-stage disease could avoid chemotherapy after surgery.

If you’ve been diagnosed with early-stage breast cancer and are weighing the pros and cons of adding chemotherapy to your treatment plan, the MammaPrint 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, such as:

  • 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!

You can learn more on the Breastcancer.org MammaPrint Test page.



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