Trastuzumab emtansine (T-DM1) is currently not yet licensed in Europe, but has received market authorisation in the U.S. based on the results of the EMILIA trial.
This phase III trial compared efficacy and safety of T-DM1 with lapatinib + capecitabine in overall 991 patients with HER2 positive advanced/metastatic breast cancer (BC). All patients had previously been treated with trastuzumab and a taxane for their metastatic disease. Progression-free survival (assessed by independent review) was the primary outcome and showed a gain of 3.2 months (HR 0.65; p<0.001) for patients treated with T-DM1 in comparison to the control group. Also, other outcomes such as overall survival (+ 5.8 months), objective response rate and median time to symptom progression favoured the T-DM1 group. Any adverse event of any grade occurred in nearly all patients in both groups, but adverse events of grade 3 or 4 were less frequent in patients treated with T-DM1 than in those treated with lapatinib + capecitabine. Dose-reductions were necessary in 27.3% of patients treated with lapatinib, in 53.4% treated with capecitabine and in 16.3% of the T-DM1 group respectively. Treatment discontinuation due to adverse events was most frequently observed with capecitabine in the safety population.
However, comparing T-DM1 with a trastuzumab-containing regimen would be of great interest, foremost because trastuzumab and T-DM1 are both manufactured by the same company, and the patent of trastuzumab expires in July 2014.