Vemurafenib, a drug originally approved for use in patients with BRAF-positive melanoma, has also shown promising anti-tumor activity in some patients harboring this same mutation in thyroid cancer, according to the results of a study published in Lancet Oncology.
The study enrolled 51 patients from around the world with progressive, radioactive iodine-refractory (RAI) papillary thyroid cancer and a BRAF mutation who were no longer responding to treatment. Participants either had never received a multi-kinase inhibitor targeting vascular endothelial growth factor receptors (Cohort 1 [VEGFR]) or had been previously treated with a VEGFR multi-kinase inhibitor (Cohort 2). Both cohorts were administered vemurafenib orally two times per day with investigator-assessed best overall response acting as the primary endpoint.
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Median follow-up time was 18.8 months for cohort 1 (n=26) and 12 months for cohort 2 (n=25). In cohort 1, ten patients experienced a partial response and an additional 9 achieved stable disease for at least 6 months, for a combined disease control rate of 73%. Median progression-free survival was 18.2 months.
In cohort 2, where patients had received more pretreatment, 6 patients had partial responses and six achieved stable disease for at least 6 months, resulting in a disease control rate of 54.5%. Overall and Median progression-free survival were 8.9 months and 14.4 months, respectively.
The rate of grade 3 or 4 adverse events reported in each group was slightly lower in cohort 1 (17 patients [65%]) than in cohort 2 (17 patients [68%]) and the most commonly reported grade 3 to 4 adverse events were squamous cell carcinoma of the skin (seven [27%] in cohort 1, five [20%] in cohort 2), lymphopenia (two [8%] in each cohort), and increased γ-glutamyltransferase (one [4%] in cohort 1, three [12%] in cohort 2).
Investigators concluded that vemurafenib demonstrated promising anti-tumor activity in patients with progressive, BRAF mutation-positive papillary thyroid cancer who had never been treated with a multi-kinase inhibitor and should be considered as a new treatment option for this patient population.
"For this group of patients, who have little to no options, that's a significant improvement," said lead author of the study, Marcia Brose, MD, PhD, Center for Rare Cancers and Personalized Therapy and Penn's Abramson Cancer Center. "This promising clinical trial is the next step in a series of trials to identify new drugs that are fundamentally shifting the horizon - improving the outcome for patients with advanced differentiated thyroid cancer."
