Pathological complete response in this parallel groups, open-label study, occurred in 51% of 152 patients in the combination treatment group, compared with 30% of the 149 patients in the trastuzumab group and 25% of the 154 patients in the lapatinib group, for an adjusted odds ratio of 2.6 for the combination vs. trastuzumab alone (Lancet 2012 Jan. 17 [doi:10.106/S0140-6736(11)61847-3]).
As in the GeparQuinto Trial, no major cardiac dysfunction occurred, and diarrhea was more frequent in the patients receiving lapatinib (23% and 21% of those in the lapatinib and combination groups, respectively, vs. 2% in the trastuzumab group who had grade 3 diarrhea).
NeoALTTO participants were enrolled between Jan. 5, 2008, and May 27, 2010, at 86 sites in 23 countries. Participants had histologically confirmed invasive HER2-positive breast cancer with tumors at least 2 cm in diameter. Lapatinib was given at 1,500 mg orally to those in the lapatinib-only group, and at 1,000 mg for those in the combination group; trastuzumab was given at a loading dose of 4 mg/m2 followed by 2 mg/kg on subsequent doses for both groups.
The anti-HER2 treatments were given alone for 6 weeks, and paclitaxel at 80 mg/m2 weekly was then added for an additional 12 weeks.
"Dual targeting of HER2-positive tumors with trastuzumab and lapatinib is undertaken because of primary and acquired resistance to both agents, their partly non-overlapping mechanisms of action, and the well characterized synergistic interaction between them in HER2 breast-cancer models," the investigators noted.
These findings provide proof of concept that dual inhibition of HER2 is better than a single-agent approach, Dr. Baselga and his colleagues said, noting that the higher pathological complete response rate for the combination was clear across all subgroups tested, which is consistent with the findings from other studies of anti-HER2 treatment in HER2-positive tumors.
"Our study also supports investigation of novel targeted agents for breast cancer in the neoadjuvant setting, when tumors have not yet acquired resistance to therapy and when chances of clinical benefit are highest," they said.
GeparQuinto was funded by GlaxoSmithKline, Roche, and Sanofi-Aventis; lapatinib was provided free of charge. Dr. Untch said he had no relevant financial disclosures, but several other GeparQuinto investigators made financial disclosures relating to these and other pharmaceutical companies. The NeoALTTO trial was funded by GlaxoSmithKline. Dr. Baselga said he has received honoraria from Roche, and his institution has received funding from GlaxoSmithKline and Roche. Several other NeoALTTO investigators made financial disclosures involving GlaxoSmithKline and/or other pharmaceutical companies. Dr. Chia, the author of the editorial that accompanied the article in the Lancet Oncology on the GeparQuinto trial, disclosed that he has received honoraria from GlaxoSmithKline, manufacturer of lapatinib, and F. Hoffmann-La Roche, manufacturer of trastuzumab, as well as an unrestricted research grant from Hoffmann-La Roche.