Randomized Study of Lapatinib Alone or in Combination With Trastuzumab in Women With ErbB2-Positive, Trastuzumab-Refractory Metastatic Breast Cancer

In the intent-to-treat population (N = 296) who received a median of three prior trastuzumab-containing regimens, the combination of lapatinib with trastuzumab was superior to lapatinib alone for PFS (hazard ratio [HR] = 0.73; 95% CI, 0.57 to 0.93; P = .008) and CBR (24.7% in the combination arm v 12.4% in the monotherapy arm; P = .01). A trend for improved OS in the combination arm was observed (HR = 0.75; 95% CI, 0.53 to 1.07; P = .106). There was no difference in ORR (10.3% in the combination arm v 6.9% in the monotherapy arm; P = .46). The most frequent adverse events were diarrhea, rash, nausea, and fatigue; diarrhea was higher in the combination arm (P = .03). The incidence of symptomatic and asymptomatic cardiac events was low (combination therapy = 2% and 3.4%; monotherapy = 0.7% and 1.4%, respectively).

Despite disease progression on prior trastuzumab-based therapy, lapatinib in combination with trastuzumab significantly improved PFS and CBR versus lapatinib alone, thus offering a chemotherapy-free option with an acceptable safety profile to patients with ErbB2-positive MBC.