Overall survival analysis of the FOXFIRE prospective randomized studies of first-line selective internal radiotherapy (SIRT) in patients with liver metastases from colorectal cancer

3507 Background: The FOXFIRE, SIRFLOX and FOXFIRE-Global (FF-SF-FFG) randomized studies evaluated the efficacy of combining first-line chemotherapy for metastatic colorectal cancer (mCRC) with selective internal radiotherapy (SIRT) using yttrium-90 resin microspheres in patients with liver metastases. The studies were designed for prospective, combined analysis of overall survival (OS). Methods: FF-SF-FFG randomized (1:1) chemotherapy-naïve mCRC patients (performance status 0/1) with liver metastases not suitable for curative resection/ablation. Arm A was oxaliplatin-based chemotherapy (mFOLFOX6/ OxMdG) ± investigator-chosen biologically targeted agent. Arm B was the same systemic therapy (oxaliplatin dose modification) + single treatment SIRT with cycle 1/2 of chemotherapy. Primary tumor in situ and/or limited extra-hepatic metastases were permitted. Minimum sample size was 1075 patients (HR 0.8, 80% power, two-sided 5% significance). Secondary outcomes included PFS, liver-specific PFS and response rate. Apart from safety, outcomes were analysed on intention-to-treat population using meta-analytic methods of pooled individual patient data. Results: Between 2006 and 2014, 1103 patients were randomized in 14 countries. Median age was 63 years (range 23-89); median follow-up 43.3 months. There were 844 deaths. There was no difference in OS (HR 1.04; 95% CI 0.90-1.19, p= 0.609) or PFS (HR 0.90, CI 0.79-1.02, p= 0.108) between Arms. Objective response rate ( p= 0.001) and liver-specific progression (HR 0.51, CI 0.43-0.62, p< 0.001) were significantly more favorable in Arm B. Patients in Arm B had higher risk of non-liver progression as first event (HR 1.98, CI 1.53-2.58, p< 0.001). Grade 3-5 adverse events were more common in Arm B (74.0%) than A (66.5%), p= 0.009. In health status questionnaires, EQ-5D utility scores were not significantly different between Arms at 6, 12 or 24 months. Conclusion: Despite higher response rates and improved liver-specific PFS, the addition of SIRT to first-line oxaliplatin-fluorouracil chemotherapy for patients with liver-only and liver-dominant mCRC did not improve OS or PFS. Clinical trial information: 83867919.