SAN FRANCISCO – Simultaneously targeting two components of the same signaling pathway in BRAF V600E–mutated biliary tract cancer is a winning strategy, suggests an analysis of the multicenter phase 2 ROAR basket trial.
Susan London/MDedge News
Dr. Zev A. Wainberg
“Recently, a number of genetic targets have been identified with distinct rates of frequency in intrahepatic, extrahepatic, and gallbladder cancer that are the subject of a number of ongoing clinical trials. In retrospective studies, mutations in BRAF have been identified in about 5%-7% of patients, predominantly in the intrahepatic cohort,” lead investigator Zev A. Wainberg, MD, noted at the 2019 GI Cancers Symposium. Previous research has shown combined inhibition of BRAF and MEK – two sequential proteins on the MAP kinase signaling pathway – to be efficacious in BRAF V600E–mutated melanoma, non–small cell lung cancer, and anaplastic thyroid cancer.
In the ROAR trial, 178 patients with advanced or metastatic BRAF V600E–mutated rare cancers who had exhausted standard treatment options were treated with the combination of the BRAF inhibitor dabrafenib (Tafinlar) and the MEK inhibitor trametinib (Mekinist). Dr. Wainberg reported results for the 35 patients having biliary tract cancer, most of whom were heavily pretreated.
With a median duration of follow-up of 8 months, the overall response rate was 42% as assessed by investigators and 36% as assessed by independent reviewers. More than half of patients had a grade 3 or 4 adverse event, but just one had to permanently stop treatment because of toxicity.
“These results represent the first prospectively analyzed cohort of patients with BRAF V600E–mutated biliary tract cancers treated with the combination of BRAF and MEK inhibition. Efficacy in this patient population with advanced disease was comparable to that of first-line chemotherapy with gemcitabine and cisplatin,” pointed out Dr. Wainberg, codirector of the GI oncology program and an assistant professor of medicine at the University of California, Los Angeles.
“Dabrafenib and trametinib demonstrated clinical benefit in patients with BRAF-mutant biliary tract cancers and should be considered a meaningful therapeutic option for these patients,” he contended. “BRAF V600E is one of several actionable driver mutations in this disease and should be considered for routine testing in patients with biliary tract cancers. In addition, among all the other data [that are] emerging in molecular analysis of this malignancy, perhaps among all the GI malignancies, this has the potential to undergo multiple studies of other targeted therapies.”
Why stop there?
“I don’t think there is anything needed to convince you that this treatment is very effective. It’s incredibly impressive,” commented invited discussant Heinz-Josef Lenz, MD, associate director for adult oncology and coleader of the gastrointestinal cancers program, University of Southern California Norris Comprehensive Cancer Center in Los Angeles.
Susan London/MDedge News
Dr. Heinz-Josef Lenz
But experience with other BRAF-mutant malignancies, such as BRAF-mutant colorectal cancer, suggests that further benefit can accrue from hitting additional molecular targets, he said. For example, rationally selected triplet combinations can suppress emergence of resistant clones up front.
“How can we do even better? I think we need to be smart in how we inhibit downstream signaling of BRAF-mutant disease,” Dr. Lenz maintained, as downstream targeting is potentially more effective. Therefore, a logical candidate for improving on the combination of BRAF and MEK inhibitors in biliary tract cancer is an ERK inhibitor. Alternatively, the combination may be synergistic when used with immune checkpoint inhibitors that target programmed death-1 or programmed death–ligand 1.
Oncologists should perform next-generation sequencing for all patients with biliary tract cancer, in Dr. Lenz’s opinion. “Biliary cancer is one of these cancers where we have many potentially actionable mutations. I know there is no drug approved, but many trials are ongoing,” he elaborated. “So I just encourage you to do that in order to identify potential trials or treatment options.”