Overall survival of patients with BRAF-mutant metastatic colorectal cancer treated with encorafenib-cetuximab in a real-world nationwide study in the Netherlands.

person Sietske C.M.W. van Nassau Department of Medical Oncology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands info_outline Sietske C.M.W. van Nassau, Koen Zwart, Frederieke van der Baan, Miriam Koopman, Anna J. van Gestel, Petur Snaebjornsson, Geraldine R. Vink, Jeanine Roodhart

Authors person Sietske C.M.W. van Nassau Department of Medical Oncology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands info_outline Sietske C.M.W. van Nassau, Koen Zwart, Frederieke van der Baan, Miriam Koopman, Anna J. van Gestel, Petur Snaebjornsson, Geraldine R. Vink, Jeanine Roodhart Organizations Department of Medical Oncology, University Medical Center Utrecht, Utrecht University, Utrecht, Netherlands, Department of Clinical Data Science, Netherlands Comprehensive Cancer Organisation (IKNL), Utrecht, Netherlands, Department of Pathology, Netherlands Cancer Institute, Amsterdam, Netherlands Abstract Disclosures Research Funding Other Foundation Zorginstituut Background: Approximately 10-15% of patients with metastatic colorectal cancer (mCRC) have BRAF V600E mutated tumors. Encorafenib plus cetuximab (EC) combination treatment was approved following the results of the randomized phase III BEACON trial and is currently recommended for all pretreated patients with BRAF V600E -mutant mCRC. Selection of patients in randomized controlled trials is based on restrictive eligibility criteria and often not representative of the patient population in daily clinical practice. Complementary real-world effectiveness studies can improve knowledge on the generalizability of trial results, and support decision making in clinical practice. Methods: This population-based study included all mCRC patients in the Netherlands treated with EC since approval in October 2020 until June 2022. Individual patient data and original pathology reports were collected. Primary endpoint was overall survival (OS), defined as time from EC initiation until death by any cause, analyzed by Kaplan-Meier curves. WebPlotDigitizer was used to reconstruct the Kaplan-Meier survival curve of the BEACON trial. Uni- and multivariable analyses were performed. Subgroup analyses were conducted for patients who would have been eligible for the BEACON trial based on key eligibility criteria: BRAF V600E mutation, 1-2 prior regimens, world health organization performance status (WHO PS) of 0-1, normal neutrophil count, absence of brain metastases, no prior RAS/RAF/MEK treatment, and no concurrent malignancies. Results: 155 patients were included with a median follow-up time of 11.1 months. Patient characteristics differed from BEACON in mean age (64 versus 60 years), primary tumor sidedness (69% versus 50% right-sided) and WHO PS (23% versus 51% WHO 0). Median OS of the total real-world cohort was 6.6 months (95% CI: 6.0-8.3) and differed significantly from BEACON (9.3 months; 95% CI: 8.0-11.3; p = 0.003). 35% of real-world patients treated with EC would not have been eligible for the BEACON trial, showing an inferior median OS of 6.0 months (95% CI: 4.6-9.2) compared to 7.0 months (95% CI: 6.4-9.8) in trial eligible real-world patients. WHO PS was independently associated with poor survival in multivariable analysis. Patients with WHO PS≥2 had a median OS of 3.9 months (95% CI: 2.4-NA) with a hazard rate of 2.5 (95% CI: 1.1-5.5; p = 0.003). Conclusions: This largest to date - unselected - population-based cohort of mCRC patients treated with EC showed an efficacy-effectiveness gap for OS. These outcomes should be considered in clinical practice for treatment decision making. Omitting EC for subgroups demonstrating very short OS, such as patients with WHO PS ≥2, needs to be considered. Further research is warranted to adapt treatment guidelines towards a more personalized approach for patients with BRAF V600E -mutated mCRC.