Figure 4.

Erlotinib can delay growth of cetuximab-resistant tumors in vivo. Mice were injected with NCI-H226 and grown to 50–100 mm³. All mice were randomized to treatment or control groups and treated with either 0.5 mg/mouse (20 mg/kg) of cetuximab or IgG intraperitoneally twice per week. Tumors were monitored for cetuximab resistance that was defined as marked tumor growth in the presence of continued cetuximab therapy. Once cetuximab-resistant tumors reached a volume >500 mm³, mice were paired according to similar time points of resistance. At this point each mouse was taken off cetuximab and treated with either vehicle (■) or 70 mg/kg of erlotinib (◊), 5 d a week by oral gavage. The black arrow designates the starting time point of erlotinib or vehicle treatment. The average tumor volume of mice treated with IgG (▴) is included in all parts for comparison purposes.