A trial looking at trastuzumab emtansine for HER2 positive breast cancer (TH3RESA)

The people who took part in this trial had HER2 positive advanced breast cancer previously treated with trastuzumab, lapatinib and a taxane chemotherapy. The researchers found that trastuzumab emtansine worked well for this group of people.

602 people took part in the trial.

• 404 had trastuzumab emtansine
• 198 had treatment recommended by their doctor

The researchers looked at the length of time it took before people’s cancer got worse. This is called progression free survival. This was:

• just over 6 months (6.2) in the group having trastuzumab emtansine
• just over 3 months (3.3) in the group having treatment recommended by their doctor

The researchers also looked at the length of time people lived after treatment. This is called overall survival. This was:

• just under 23 months (22.7) in the group having trastuzumab emtansine
• just under 16 months (15.8) in the group having treatment recommended by their doctor

They looked at the side effects people had in both groups and how severe these side effects were. People having trastuzumab emtansine had less severe side effects.

The most common side effects of trastuzumab emtansine were:

• tiredness (fatigue)
• weakness and lacking energy
• a reduction in the number of platelets in the blood (thrombocytopenia), these help the blood to clot

The most common side effects from the treatment chosen by doctors included:

• tiredness (fatigue)
• a reduction in the number of white blood cells in the blood (neutropenia), these help to fight infection
• diarrhoea

The researchers concluded that trastuzumab emtansine should be used as a standard treatment  for people with advanced HER 2 positive breast cancers who have had previous treatment.