FOLFIRI plus cetuximab versus FOLFIRI plus bevacizumab for metastatic colorectal cancer (FIRE-3): a post-hoc analysis of tumour dynamics in the final RAS wild-type subgroup of this randomised open-label phase 3 trial.

BACKGROUND: FIRE-3 compared first-line 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI) plus cetuximab with FOLFIRI plus bevacizumab in patients with KRAS exon 2 wild-type metastatic colorectal cancer. The same study also reported an exploratory analysis of a subgroup of patients with tumours that were wild-type at other RAS genes (KRAS and NRAS exons 2-4). We report here efficacy results for the FIRE-3 final RAS (KRAS/NRAS, exons 2-4) wild-type subgroup. Moreover, new metrics of tumour dynamics were explored during a centralised radiological review to investigate how FOLFIRI plus cetuximab conferred overall survival benefit in the absence of differences in investigator-assessed objective responses and progression-free survival. METHODS: FIRE-3 was a randomised phase 3 trial comparing FOLFIRI plus cetuximab with FOLFIRI plus bevacizumab in the first-line treatment of patients with KRAS exon 2 wild-type metastatic colorectal cancer. The primary endpoint of the FIRE-3 study was the proportion of patients achieving an objective response according to Response Evaluation Criteria In Solid Tumors (RECIST) 1.0 in the intention-to-treat population. A centralised radiological review of CT scans was done in a post-hoc analysis to assess objective response according to RECIST 1.1, early tumour shrinkage, depth of response, duration of response, and time to response in the final RAS wild-type subgroup. Comparisons between treatment groups with respect to objective response rate and early tumour shrinkage were made using Fisher's exact test (two-sided), while differences in depth of response were investigated with a two-sided Wilcoxon test. This trial is registered at ClinicalTrials.gov, number NCT00433927. FINDINGS: In the final RAS wild-type population (n=400), median overall survival was better in the FOLFIRI plus cetuximab group than the FOLFIRI plus bevacizumab group (33·1 months [95% CI 24·5-39·4] vs 25·0 months [23·0-28·1]; hazard ratio 0·70 [0·54-0·90]; p=0·0059), although investigator-assessed objective response and progression-free survival were comparable between treatment groups. Centralised radiological review of CT-assessable patients (n=330) showed that the proportion of patients achieving an objective response (113 of 157, 72·0% [95% CI 64·3-78·8] vs 97 of 173, 56·1% [48·3-63·6]; p=0·0029), frequency of early tumour shrinkage (107 of 157, 68·2% [60·3-75·4] vs 85 of 173, 49·1% [41·5-56·8]; p=0·0005), and median depth of response (-48·9% [-54·3 to -42·0] vs -32·3% [-38·2 to -29·2]; p<0·0001) were significantly better in extended RAS wild-type patients receiving FOLFIRI plus cetuximab versus those receiving FOLFIRI plus bevacizumab. No differences in duration of response and time to response were observed between treatment groups. INTERPRETATION: This analysis provides a new framework that connects alternative metrics of response to overall survival. Superior response-related outcome parameters, such as early tumour shrinkage and depth of response, obtained by centralised radiological review correlated with the overall survival benefit conferred by FOLFIRI plus cetuximab compared with FOLFIRI plus bevacizumab in the extended RAS wild-type subgroup. FUNDING: Merck KGaA and Pfizer.

FOLFIRI plus cetuximab versus FOLFIRI plus bevacizumab as first-line treatment for patients with metastatic colorectal cancer (FIRE-3): a randomised, open-label, phase 3 trial.

BACKGROUND: Cetuximab and bevacizumab have both been shown to improve outcomes in patients with metastatic colorectal cancer when added to chemotherapy regimens; however, their comparative effectiveness when partnered with first-line fluorouracil, folinic acid, and irinotecan (FOLFIRI) is unknown. We aimed to compare these agents in patients with KRAS (exon 2) codon 12/13 wild-type metastatic colorectal cancer. METHODS: In this open-label, randomised, phase 3 trial, we recruited patients aged 18-75 years with stage IV, histologically confirmed colorectal cancer, an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2, an estimated life expectancy of greater than 3 months, and adequate organ function, from centres in Germany and Austria. Patients were centrally randomised by fax (1:1) to FOLFIRI plus cetuximab or FOLFIRI plus bevacizumab (using permuted blocks of randomly varying size), stratified according to ECOG performance status, number of metastatic sites, white blood cell count, and alkaline phosphatase concentration. The primary endpoint was objective response analysed by intention to treat. The study has completed recruitment, but follow-up of participants is ongoing. The trial is registered with ClinicalTrials.gov, number NCT00433927. FINDINGS: Between Jan 23, 2007, and Sept 19, 2012, 592 patients with KRAS exon 2 wild-type tumours were randomly assigned and received treatment (297 in the FOLFIRI plus cetuximab group and 295 in the FOLFIRI plus bevacizumab group). 184 (62·0%, 95% CI 56·2-67·5) patients in the cetuximab group achieved an objective response compared with 171 (58·0%, 52·1-63·7) in the bevacizumab group (odds ratio 1·18, 95% CI 0·85-1·64; p=0·18). Median progression-free survival was 10·0 months (95% CI 8·8-10·8) in the cetuximab group and 10·3 months (9·8-11·3) in the bevacizumab group (hazard ratio [HR] 1·06, 95% CI 0·88-1·26; p=0·55); however, median overall survival was 28·7 months (95% CI 24·0-36·6) in the cetuximab group compared with 25·0 months (22·7-27·6) in the bevacizumab group (HR 0·77, 95% CI 0·62-0·96; p=0·017). Safety profiles were consistent with the known side-effects of the study drugs. The most common grade 3 or worse adverse events in both treatment groups were haematotoxicity (73 [25%] of 297 patients in the cetuximab group vs 62 [21%] of 295 patients in the bevacizumab group), skin reactions (77 [26%] vs six [2%]), and diarrhoea (34 [11%] vs 40 [14%]). INTERPRETATION: Although the proportion of patients who achieved an objective response did not significantly differ between the FOLFIRI plus cetuximab and FOLFIRI plus bevacizumab groups, the association with longer overall survival suggests that FOLFIRI plus cetuximab could be the preferred first-line regimen for patients with KRAS exon 2 wild-type metastatic colorectal cancer. FUNDING: Merck KGaA.