Aflibercept-Based and Bevacizumab-Based Second Line Regimens in Patients with Metastatic Colorectal Cancer: Propensity Score Weighted-Analysis from a Multicenter Cohort

Background: Both aflibercept and bevacizumab-based regimens are available II-line treatment options for patients with metastatic colorectal cancer (mCRC). However, no head-to-head trials established the optimal anti-angiogenic strategy for this setting. Methods: We launched a multicenter, retrospective, observational study to assess and compare clinical efficacy of II-line treatments for patients with mCRC. Patients with KRAS/NRAS/BRAF-wild type and KRAS/NRAS mutant tumors were also analyzed separately. Findings: 348 patients were included, of whom 153 and 195 were treated with bevacizumab- and aflibercept-based regimens, respectively. Patients treated with aflibercept showed an increased risk of death (corrected [co]-HR 1.92, 95 %CI: 1.37–2.68), of disease progression/death (co-HR 1.43, 95 %CI: 1.12–1.82) and a decreased objective response rate (ORR) (21.5 % vs 34.7 %, p=0.007) in comparison to bevacizumab. Patients treated with II-line bevacizumab were more frequently treated in the third line setting after disease progression (91.1 % vs 68.5 %, p<0.0001). In the KRAS/NRAS mutant cohort, treatment with bevacizumab was associated with longer overall survival (OS) (18.0 months vs 12.5 months, p=0.0069), but similar progression free survival (PFS) (p=0.32) and ORR (p=0.57). In the KRAS/NRAS, BRAF wild type cohort, patients treated with bevacizumab achieved longer OS (20.2 months vs 10.6 months, p=0.013), PFS (8.4 months vs 3.7 months, p=0.0002), and higher ORR (48.6 % vs 15.0 %, p=0.0016), compared to those treated with aflibercept. The results were independently confirmed with inverse probability of treatment weighting and with fixed multivariable Cox-regressions. Conclusion: These findings support the use of bevacizumab-based over aflibercept-based regimens as II-line treatment in mCRC, especially in KRAS/NRAS and BRAF wild type tumors.