EGFR and neoplasm: Sidedness was a significant determinant of benefit, with EGFR mAb use associated with PFS prolongation in left-side tumours but not right-sided disease (left-sided PFS HRadj 0.74, 95% CI 0.67–i0.83, p < 0.001; right-sided PFS HRadj 1.03, 95% CI 0.81–1.32, p = 0.798, pinteraction 0.021).