Withholding the Introduction of Anti-Epidermal Growth Factor Receptor: Impact on Outcomes in RAS Wild-Type Metastatic Colorectal Tumors: A Multicenter AGEO Study (the WAIT or ACT Study)

Background: Patients with RAS wild-type (WT) nonresectable metastatic colorectal cancer (mCRC) may receive either bevacizumab or an anti-epidermal growth factor receptor (EGFR) combined with first-line, 5-fluorouracil-based chemotherapy. Without the RAS status information, the oncologist can either start chemotherapy with bevacizumab or wait for the introduction of the anti-EGFR. Our objective was to compare both strategies in a routine practice setting.

Materials and methods: This multicenter, retrospective, propensity score-weighted study included patients with a RAS WT nonresectable mCRC, treated between 2013 and 2016 by a 5-FU-based chemotherapy, with either delayed anti-EGFR or immediate anti-vascular endothelial growth factor (VEGF). Primary criterion was overall survival (OS). Secondary criteria were progression-free survival (PFS) and objective response rate (ORR).

Results: A total of 262 patients (129 in the anti-VEGF group and 133 in the anti-EGFR group) were included. Patients receiving an anti-VEGF were more often men (68% vs. 56%), with more metastatic sites (>2 sites: 15% vs. 9%). The median delay to obtain the RAS status was 19 days (interquartile range: 13-26). Median OS was not significantly different in the two groups (29 vs. 30.5 months, p = .299), even after weighting on the propensity score (hazard ratio [HR] = 0.86, 95% confidence interval [CI], 0.69-1.08, p = .2024). The delayed introduction of anti-EGFR was associated with better median PFS (13.8 vs. 11.0 months, p = .0244), even after weighting on the propensity score (HR = 0.74, 95% CI, 0.61-0.90, p = .0024). ORR was significantly higher in the anti-EGFR group (66.7% vs. 45.6%, p = .0007).

Conclusion: Delayed introduction of anti-EGFR had no deleterious effect on OS, PFS, and ORR, compared with doublet chemotherapy with anti-VEGF.

Implications for practice: For RAS/RAF wild-type metastatic colorectal cancer, patients may receive 5-fluorouracil-based chemotherapy plus either bevacizumab or an anti-epidermal growth factor receptor (EGFR). In daily practice, the time to obtain the RAS status might be long enough to consider two options: to start the chemotherapy with bevacizumab, or to start without a targeted therapy and to add the anti-EGFR at reception of the RAS status. This study found no deleterious effect of the delayed introduction of an anti-EGFR on survival, compared with the introduction of an anti-vascular endothelial growth factor from cycle 1. It is possible to wait one or two cycles to introduce the anti-EGFR while waiting for RAS status.