Impact of first-line bevacizumab therapy on the efficacy of subsequent anti-epidermal growth factor antibodies (anti-EGFR) in metastatic colorectal cancer (mCRC).

Abstract

685 Background: The FIRE3 study reported that cetuximab added to first line combination chemotherapy versus the addition of bevacizumab to the same chemotherapy backbone, with a planned switch to the alternative biologic in second line therapy, resulted in improved overall survival. One possible explanation is that the sequence of biologic administration in mCRC impacts on treatment benefit. Examination of the efficacy of anti-EGFR therapy in cohorts where patients have and have not received prior bevacizumab will inform this. Methods: We interrogated our prospective database (ACCORD), which records comprehensive detail on demographics, treatments received and patient outcomes for consecutive mCRC patients in real world practice across multiple institutions in Australia. We included patients receiving 2nd and subsequent line anti-EGFR monotherapy. Disease control rate (DCR) (partial response plus stable disease), progression free survival (PFS) and overall survival (OS) from the start of anti-EGFR were determined as a function of prior bevacizumab use. Results: From a total of 1511 patients treated between 01/10/2002 and 31/12/2014,129 patients treated with single agent anti- EGFR were identified, 75 had received prior bevacizumab. Demographics, performance status and tumour characteristics were similar between the 2 groups. 84% were confirmed KRAS exon 2 wild type. Prior treatment with bevacizumab did not impact DCR (35% vs 40%, p = 0.5065), median PFS (3.0 vs 3.0 months, p = 0.9460) or OS (8.6 vs 8.4 months, HR 0.95, p = 0.8073). Similarly, for bevacizumab treated patients, the time since last dose of bevacizumab to start of anti-EGFR ( < 3 months (n = 26) vs 3-6 months (n = 17) vs > 6 months (n = 32)) did not impact PFS (2.3 vs 3.6 vs 3 months) or OS (8.9 vs 10.1 vs 7.1 months, HR: 0.88, p = 0.82). Conclusions: There was no evident impact of previous bevacizumab treatment, or time from previous bevacizumab treatment, on the efficacy of single agent anti-EGFR therapy in a routine clinical practice cohort. Our data do not support the notion that prior bevacizumab renders tumors more or less sensitive to subsequent anti EGFR therapy.