ARRB1 and neoplasm: However, when analysing beta-arrestin-1 plasma levels according to tumour response to EGFR inhibitors (here CR and PR were combined in one group, since only 2 patients achieved CR; n = 11), we observed a trend towards increased beta-arrestin-1 baseline levels with worsening responses (a significant difference between patients with PD (n = 14) after EGFR inhibitor treatment and patients in the CR+PR group was shown (P value = 0.0173)) (Supplementary Figure 5B).