Real world characteristics and outcomes of patients with BRAFV600E-mutant metastatic colorectal cancer in Australia: The COALA project.

70 Background: BRAFV600E-mutant metastatic colorectal cancer (mCRC) represents a unique molecular subset with poor prognosis and less responsiveness to chemotherapy. The BEACON CRC study demonstrated that encorafenib plus cetuximab (EC) significantly improved overall survival (OS) compared to FOLFIRI plus cetuximab in BRAF-mutant mCRC as 2 nd or 3 rd line therapy. This combination was reimbursed in Australia from January 2022. Methods: We analysed data from the Australian TRACC mCRC clinical registry, encompassing patients (pts) with BRAF-mutant mCRC diagnosed in Australia from 2009 to 2024 at 31 hospitals. We assessed baseline demographics, uptake of EC following reimbursement and efficacy analysis of progression-free survival (PFS) and OS for pts that received EC and those who did not. Pts receiving EC on a clinical trial were excluded. Results: Among 2,800 pts with known BRAF mutation status, 365 (13%) were BRAF mutated. The BRAF mutant cohort had a median age of 63 years, with a significantly higher mutation rate in the 20-39 age group than other age groups (age 20-39, 25.5%; age 40-59, 10%; age 60+, 13.2%; P<0.001); 54.5% were female, 58% right-sided tumours, 64% with synchronous metastatic disease and 21.7% deficient mismatch repair (dMMR). Overall, 314 (86%) pts with BRAF mutant tumours and 2,079 (85%) BRAF wild-type (WT) tumours received 1 st line treatment, and 156 (43%) BRAF mutant and 1,144 (47%) BRAF WT pts received 2 nd line therapy. The median OS from diagnosis was 17.3 months for BRAF mutant pts versus 34.7 months for BRAF WT pts (p < 0.0001). All dMMR BRAF mutant pts received 1 st line pembrolizumab since its reimbursement in August 2021. Among 41 BRAF mutant pts progressing on 1 st line therapy since January 2022,(32 pMMR, 9 dMMR), 33 (80%) were subsequently treated with EC, and 4 (10%) did not receive further treatment. OS from the start of 2 nd line therapy was 9.6 months (95% CI: 7.2-12.5) for pts who received EC and 7.1 months (95% CI: 6.4-8.6) for those who received other systemic treatment. Median PFS for pts receiving EC was 4.6 months (95% CI: 3.4-5.8) and 3.3 months (95% CI: 2.5-5.3) for other 2 nd line treatments. Conclusions: mCRC pts younger than 40 have a high rate of BRAF mutation, where 1 in 4 tumours harbour the mutation. BRAF mutant mCRC has a poorer outcome than BRAF WT despite a similar proportion receiving 1 st and 2 nd line treatment. The majority of eligible BRAF mutant mCRC pts received EC following reimbursement in Australia, with PFS and OS outcomes consistent with the BEACON CRC trial.