MARIANNE Trial Shows T-DM1 Works About As Well As Standard First Treatment for HER2-Positive Metastatic Breast Cancer

Breast Cancer News
January 21, 2015
Erin Rowley, Writer and Content Coordinator
Reviewed By: 
Carey K. Anders, MD

At the end of 2014, the pharmaceutical company Genentech announced results from the phase III MARIANNE trial. These results show that T-DM1, with or without pertuzumabinfo-icon, works about as well as, but not significantly better than, the standard treatment for people newly diagnosed with HER2-positive metastaticinfo-icon breast cancer. Both T-DM1 and pertuzumab are sold by Genentech. The final results of MARIANNE will be presented at a future medical meeting and are not yet published in a medical journal.

Background and Goals

T-DM1 (Kadcyla) is an anti-body drug conjugate, a cancer medicineinfo-icon that pairs chemotherapyinfo-icon with a targeted therapyinfo-icon. This delivers the chemotherapy to tumorinfo-icon cells more directly and lessens harmful effects on healthy cells.

The targeted therapy used in T-DM1 is trastuzumabinfo-icon (Herceptininfo-icon). Trastuzumab is a standard treatment for HER2 (human epidermal growth factor receptor 2info-icon)-positive breast cancer. Breast cancer is HER2-positive when breast cells have too many HER2 proteins or geneinfo-icon copies, which cause cells to grow faster than they should.

T-DM1 is FDAinfo-icon-approved for use in metastatic HER2-positive breast cancer that has continued to grow despite use of other treatments. Pertuzumab (Perjeta), another treatment for HER2-positive metastatic breast cancer, is FDA-approved for use with trastuzumab and chemotherapy for people with HER2-positive metastatic breast cancer who have not had treatment for metastatic disease before.

Researchers with the MARIANNE trial wanted to learn if using T-DM1 alone, or with pertuzumab, would work better than the standard treatment: trastuzumab plus chemotherapy.


The MARIANNE trial involved 1,095 people with metastatic breast cancer who had not already been treated for metastatic disease. They were randomly chosen to receive

  • T-DM1 alone
  • T-DM1 plus pertuzumab
  • Trastuzumab plus chemotherapy (either docetaxelinfo-icon or paclitaxelinfo-icon)

The main result researchers looked at was progression-free survivalinfo-icon, PFS, the time from the start of treatment until the disease gets worse, or until death.


Neither group that received T-DM1 had significantly longer progression-free survival than the group that received trastuzumab plus chemotherapy.

More specific data from the trial will be released in the near future.

What This Means for You

It can be disappointing when a medicine proves not to be as effective as researchers hoped it would be. However, these results do not change the fact that T-DM1 is FDA-approved to treat HER2-positive metastatic breast cancer that has continued to grow after the use of other treatments. It also doesn’t change the fact that pertuzumab, when combined with trastuzumab and chemotherapy, is FDA-approved for previously untreated HER2-positive metastatic breast cancer.

T-DM1 is still an important treatment; it’s just unlikely that it will be the first treatment a person with HER2-positive metastatic breast cancer gets.

Clinicalinfo-icon trials like MARIANNE help doctors learn what works, and what doesn’t work, when treating breast cancer. To help them learn more, consider taking part in a clinical trialinfo-icon. For more information, talk to your doctor and visit

Read more about MARIANNE on

Additional Related Topics 
Targeted Therapy