Efficacy and safety of dabrafenib (D) and trametinib (T) in patients (pts) with BRAF V600E–mutated biliary tract cancer (BTC): A cohort of the ROAR basket trial.

187Background: BTCs are rare, aggressive malignancies with poor prognoses. Treatment options and outcomes after first-line therapy are not well defined. Median progression-free survival (PFS) in second-line BTC is < 5 mo. Combined BRAF + MEK inhibition is efficacious in BRAF V600–mutated anaplastic thyroid cancer, melanoma, and lung cancer, but less so in BRAF V600E-mutated colorectal cancer. Activating BRAF V600E mutations have been reported in 0% to 20% of BTCs; thus, D (BRAF inhibitor) + T (MEK inhibitor) was evaluated as a treatment for pts with BRAF V600E–mutated BTC in the ROAR basket trial. Methods: In this phase II, open-label trial, pts with BRAF V600E mutations in 9 rare tumor types, including BTC, received D (150 mg BID) + T (2 mg QD) until unacceptable toxicity, disease progression, or death. Eligible pts had advanced or metastatic cancer and had been treated with ≥ 1 prior systemic therapy. The primary endpoint was investigator-assessed overall response rate (ORR). Secondary endpoints include...