Pharmacodynamic study of neoadjuvant vemurafenib (VEM) in patients (pts) with BRAF mutated, locally advanced papillary thyroid cancer (PTC).

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TPS6100 Background: BRAF mutations are found in 40% of pts with newly diagnosed PTC but much more prevalent in recurrent PTC, ranging from 78-86%, suggesting they play an active role in tumor progression. Activating mutations in BRAF result in constitutive activation of MEK and subsequently ERK. ERK mediates activation of nuclear transcription factors coordinating expression of genes involved in proliferation and survival of malignant cells. PTC usually has an excellent prognosis, especially in younger pts and in pts who respond to the only effective treatment: surgery followed by radioactive iodine (RAI). However, more advanced stage disease at diagnosis, older age, and lack of RAI avidity are associated with a high rate of recurrence and distant metastasis, imparting a worse overall survival. Long-term outcomes depend highly on initial surgery outcome. Pts at highest risk of recurrence and death are those with gross residual disease after surgery and macroscopic tumor invasion. VEM is an inhibitor of the activated form of the BRAF serine-threonine kinase enzyme. The drug is FDA approved for the treatment of advanced melanoma and is currently being studied in a phase 2 trial in metastatic BRAF-mutated PTC. This is a neoadjuvant trial to determine if pharmacodynamic changes in the tumor correlate with response to drug. Methods: Pts with primary or recurrent BRAF mutated PTC who are planned for surgical resection are eligible. Pts will undergo baseline core biopsy prior to starting VEM 960mg bid. After 56 days of treatment they will undergo surgery and post-treatment specimen will be collected. Pts with widely metastatic PTC may continue VEM. The primary endpoint is to determine whether changes in ERK phosphorylation responses after treatment with VEM correlate with clinical response at day 56 in pts with locally advanced, BRAF mutated PTC. Secondary endpoints include assessments of safety of neoadjuvant VEM, response by RECIST, rate of surgical complications, persistent disease at the surgical site at 1 year, and mechanisms of resistance to VEM. The trial began enrolling pts in December 2012, with a total of 22 pts planned. This trial has no sponsor. Clinical trial information: NCT01709292.