T-DM1 Improves Survival in Women With HER2-Positive Metastatic Breast Cancer

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New results from the EMILIA study show that women diagnosed with HER2-positive metastatic breast cancer that had stopped responding to a standard targeted therapy regimen lived longer with or without the cancer growing (overall survival) when they got the experimental medicine T-DM1 (chemical name: ado-trastuzumab emtansine) compared to women who got a different targeted therapy regimen.

The results were reported by Genentech, the company that makes T-DM1, and will be presented at an upcoming professional meeting.

T-DM1 is a combination of the targeted therapy medicine Herceptin (chemical name: trastuzumab) and the chemotherapy medicine emtansine. In T-DM1, the emtansine is attached to the Herceptin.

(In earlier studies on T-DM1, it was reported that the chemotherapy medicine maytansine was attached to Herceptin to form T-DM1. Emtansine is a derivative of maytansine.)

Herceptin is approved by the U.S. Food and Drug Administration (FDA) to treat advanced stage, HER2-positive breast cancers and to lower the risk of recurrence of early-stage, HER2-positive breast cancer with a high risk of recurrence. HER2-positive breast cancers make too much of the HER2 protein. The HER2 protein sits on the surface of cancer cells and receives signals that tell the cancer to grow and spread. About one out of every four breast cancers is HER2-positive. Herceptin works by attaching to the HER2 protein and blocking it from receiving growth signals.

Emtansine, like some other chemotherapy medicines, disrupts the way cells grow. Emtansine isn’t a targeted medicine, which means it can affect healthy cells as well as cancer cells.

T-DM1 was designed to deliver emtansine to cancer cells in a targeted way by attaching emtansine to Herceptin. Herceptin then carries emtansine to the HER2-positive cancer cells.

Metastatic breast cancer is breast cancer that has spread to other parts of the body away from the breast, such as the bones or liver.

The EMILIA study looked at 991 women diagnosed with either metastatic or locally advanced HER2-positive breast cancer that had stopped responding to a standard treatment regimen of Herceptin and a taxane chemotherapy. Paclitaxel (brand name: Taxol), albumin-bound or nab-paclitaxel (brand name: Abraxane), and docetaxel (brand name: Taxotere) are taxanes. Locally advanced breast cancer is cancer that has spread to the chest wall below or the skin above the breast.

The women were randomly assigned to receive one of two treatment regimens:

  • half the women got a combination of the targeted therapy Tykerb (chemical name: lapatinib) and the chemotherapy Xeloda (chemical name: capecitabine); this combination already is approved to treat advanced-stage HER2-positive breast cancer that has stopped responding to Herceptin
  • half the women got T-DM1

Half the women were followed for more than a year and the other half were followed for shorter times.

Overall survival – the time the women lived with or without the cancer growing – was longer for women treated with T-DM1 compared to women treated with Tykerb and Xeloda. Because the results haven’t been presented at a conference yet, Genentech hasn’t released the specific numbers.

Earlier results from the EMILIA study found that progression-free survival – the time the women lived without the cancer growing – was longer for women treated with T-DM1 (9.6 months) compared to women treated with Tykerb and Xeloda (6.4 months).

Severe side effects are unfortunately common with many cancer treatments. About 41% of women who got T-DM1 had severe side effects compared to 57% of women who got the Tykerb-Xeloda combination.

The results suggest that T-DM1 could be an important new treatment option for women diagnosed with advanced-stage, HER2-positive breast cancer. Genentech has applied for FDA approval for T-DM1.

If you’ve been diagnosed with locally advanced or metastatic HER2-positive breast cancer, you and your doctor may be considering a number of treatment options. If you’re willing to participate in a clinical trial, you may have even more options available, possibly including an experimental medicine such as T-DM1. Talk to your doctor about clinical trials that might be a good fit for you and your unique situation. Visit the Breastcancer.org Clinical Trials pages for more information.

And stay tuned to Breastcancer.org for updates on the approval process for T-DM1.

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