Trastuzumab emtansine (T-DM1) significantly improved overall survival of persons with HER2-positive metastatic breast cancer compared with the combination treatment of lapatinib and capecitabine, according to updated results from the drug company testing T-DM1.

A previous interim analysis demonstrated a trend toward improved overall survival in patients receiving T-DM1 compared with those on the lapatinib-plus-Xeloda regimen, but the data were not considered statistically significant at that time. Now, the new confirmatory analysis of overall survival has crossed a prespecified boundary showing that T-DM1 significantly extended survival compared with the other treatment.

Pharmaceutical company Roche (Basel, Switzerland) announced in a press release that new data from the international, phase III EMILIA study shows participants have now met both primary efficacy endpoints of significant improvements in overall survival and progression-free survival. The trial involves 991 persons with HER2-positive locally advanced or metastatic breast cancer who had previously undergone treatment with Herceptin (trastuzumab) and taxane chemotherapy.

Half the group (495 patients) was assigned to receive T-DM1, an antibody-drug conjugate (ADC) under study. Comprised of the antibody trastuzumab and the chemotherapy DM1, T-DM1 is designed to target and inhibit HER2 signaling and deliver DM1 directly inside HER2-positive cancer cells. People in the lapatinib-and-capecitabine arm of the EMILIA study now will be offered the option to receive T-DM1.

Although the Roche statement provided no statistics on overall survival, EMILIA data released in June 2012 showed that among 495 persons given T-DM1, risk of disease progression was 35% lower than that seen among the 496 patients receiving lapatinib plus capecitabine (median progression-free survival 9.6 months vs 6.4 months). In addition, fewer adverse effects of grade 3 or higher were seen in the T-DM1 group.

Genentech, a member of the Roche Group, licenses technology for T-DM1 under an agreement with ImmunoGen, Inc., and has submitted a Biologics License Application for the agent to the FDA. Genentech also manufactures capecitabine under the brand name Xeloda.