Evaluating the Optimal Sequence of Treatment With EGFR Inhibitors and Bevacizumab in RAS Wild-Type Metastatic Colorectal Cancer

Background Epithelial growth factor receptor inhibitors (EGFRi) and bevacizumab are the two main target therapies available for first-line treatment of RAS wild-type (wt) metastatic colorectal cancer (mCRC). However, the optimal sequencing of these agents remains unclear. In this study, we aimed to evaluate the optimal sequence with EGFRi and bevacizumab in first- and second-line treatment. Methods This was a retrospective cohort study with RAS wt mCRC patients identified by extended RAS analysis between 2013 and 2020 at a comprehensive cancer center. All patients had to be treated with a sequence of systemic treatment that included an EGFRi and bevacizumab in first and second line, in either order. Two groups were defined according to treatment sequence: first-line EGFRi followed by second-line bevacizumab (cohort A) or the reverse sequence (cohort B). Primary endpoint was overall survival (OS). Secondary endpoints were progression-free survival with first-line treatment (PFS1), progression-free survival with second-line treatment (PFS2), objective response rate (ORR), and serious adverse events (grade >= 3). Survival was estimated using the Kaplan-Meier method, and survival differences between groups were compared using the log-rank test. Univariate analyses were performed using Cox proportional hazard model. Results A total of 124 patients were included (93 in cohort A and 31 in cohort B). There were no statistical significant differences in median OS (A: 34.9 months vs B: 29.2 months; p=0.590), PFS1 (A: 13.1 months vs B: 8.2 months; p=0.600), and PFS2 (A: 7.4 months vs B: 5.5 months; p=0.110) between groups. No significant differences were also found between treatment sequences in subgroups defined by age, gender, primary tumor location, sidedness, timing of metastasis, number of metastatic sites, multimodal therapy, primary tumor resection, and first-line chemotherapy backbone. ORR was significantly higher with first-line treatment with EGFRi (A: 55.9% vs B: 22.6%; p=0.001). At the final follow-up, the proportion of patients with SAEs was similar between treatment sequences (p=0.827). Discussion Our study showed no impact of the treatment sequence with EGFRi and bevacizumab in the survival of RAS wt mCRC. However, patients treated with first-line EGFRi had significantly higher response rates, thus favoring its use in patients with symptomatic tumors and borderline resectable metastasis. Prospective trials are warranted to define the optimal sequence of treatment in RAS wt mCRC patients.