Antitumour activity of erlotinib and cetuximab on Calu-3 xenografts. Calu-3 cells were suspended in matrigel and sterile PBS (1:1) and implanted s.c. (right flank) on female BALB/c-Nude mice. Tumours were allowed to establish growth after implantation for 14 days, and the treatments started when tumours reached an average volume of 300 mm3. Vehicle, erlotinib (25 mg/Kg, orally 5 days/week), cetuximab (2 mg/Kg i.p. twice weekly), or erlotinib plus cetuximab were administered for the duration of the study. Data are expressed as percent change in tumour volume ± SEM of 6 mice per group. (**p < 0.01, ***p < 0.001 vs control; #p < 0.05, ###p < 0.001 vs erlotinib; §p < 0.05 vs cetuximab; two-way ANOVA followed by Bonferroni post-test).