Vemurafenib for the Treatment of Patients with BRAF V600E-Positive Papillary Thyroid Cancer

Patients with papillary thyroid cancer (PTC) who develop metastatic, radioactive iodine (RAI)-refractory, progressive and/or symptomatic disease require a more aggressive approach. BRAF V600E mutations are found in approximately 40% of primary PTC tumors and up to 70% of recurrent PTC. Vemurafenib, a selective BRAF inhibitor, has shown promising clinical activity; recently reported results of three patients in phase I trial had shown that one patient had a confirmed partial response and two had stable disease.

A team of researchers from MD Anderson Cancer Center and Baylor College of Medicine, in Houston, TX, conducted a case series of BRAF V600E-positive PTC patients treated outside a clinical trial with vemurafenib. They concluded that in patients with metastatic, progressive, RAI-refractory PTC harboring BRAF V600E mutation, vemurafenib is an effective and well tolerated treatment strategy even when used outside of a clinical trial, as presented at the 83rd Annual Meeting of the American Thyroid Association, in San Juan, Puerto Rico, on October 19, 2013.

For this study, 12 patients (median age at diagnosis: 62 years) receiving vemurafenib were evaluated, all of which had BRAF V600E positivity by DNA testing. All patients had RAI non-avid disease. At the start of vemurafenib treatment, site of distant metastases included lung in 75% of patients and bone in 40% of patients. The median time on treatment was 20 weeks.

Best response was evaluated using RECIST v.1.1: partial response ≥ 30% reduction in the sum of target lesions; progressive disease ≥ 20% increase in the sum of target lesions; and stable disease was any percentage of change between +19% and —29%. Minor response was defined as 10% to 29% tumor size reduction. A single radiologist reviewed all images.

For the study, 3 of 12 patients (25%) had a partial response to treatment and 75% had stable disease, of which five out of nine patients had minor response to treatment. The study is ongoing with 11 patients. No progression was noted at the time of the presentation.

Vemurafenib starting dose was 960 mg twice daily. Drug hold was needed in 75% of patients and dose reduction in 50% of patients. Adverse events were evaluated using CTCAE v.4.0, and the most common were skin rash (50%), anorexia (50%), fatigue (50%), diarrhea (42%), photosensitivity (42%), verrucous keratosis (42%), weight loss (42%), arthralgias (25%), hand foot syndrome (25%), and hair loss (25%).

With this study, the authors confirmed similar results to those reported in a recent phase II trial.