Tumor-agnostic efficacy and safety of dabrafenib plus trametinib in BRAFV600E-mutated rare cancers: ROAR basket study

Abstract

Beyond melanoma, BRAFV600E alterations are prevalent across multiple tumors. We conducted a basket trial (NCT02034110) to assess efficacy and safety of oral BRAF inhibitor dabrafenib (150 mg BD) plus MEK inhibitor trametinib (2 mg OD) in 206 patients (eight cohorts) with BRAFV600E-mutated advanced rare cancers. Patients with anaplastic carcinoma thyroid, biliary tract cancer, gastrointestinal stromal tumor, adenocarcinoma of small intestine, low-grade (eight histologies)/high-grade (seven histologies) glioma, hairy cell leukemia, and multiple myeloma were treated until unacceptable toxicity, disease progression, or death. Overall, median duration of exposure to dabrafenib and trametinib was 12.5 (1–82) and 12.0 (1–84) months, respectively. Primary endpoint was tumor response; secondary endpoints were duration of response, progression free and overall survival, and safety (investigator-assessed). Overall response rate was 56% (38.1%, 72.1%), 53% (37.7%, 68.8%), 0%, 67% (9.4%, 99.2%), 54% (25.1%, 80.8%), 33% (20.0%, 49.0%), 89% (77.8%, 95.9%), and 50% (18.7%, 81.3%), respectively. Median (95% confidence interval) duration of response was 14.4 (7.4, not reached), 8.9 (5.6, 13.7), not reached, 7.7 (not reached, not reached), not reached (5.5, not reached), 31.2 (7.4, 44.2), not reached, and 11.1 (5.6, not reached) months, respectively. Durable and clinically meaningful responses were observed in solid and hematological malignancies (21 histologies). Safety profile was acceptable; most frequent (≥20% patients) treatment-related adverse events were pyrexia (40.8%), fatigue (25.7%), chills (25.7%), nausea (23.8%), and rash (20.4%). The encouraging tumor-agnostic activity of dabrafenib plus trametinib is a promising approach in patients with BRAFV600E-mutated advanced rare cancers. These results supported the accelerated FDA approval for a tumor-agnostic BRAF+MEK inhibitor combination representing a precision medicine milestone.