LAUSR

Dabrafenib, a BRAF selective tyrosine kinase inhibitor (TKI) has been associated with pancreatitis alone, and in combination with trametinib (a MEK pathway inhibitor). We report a case of dabrafenib induced acute pancreatitis in a patient undergoing treatment for metastatic papillary thyroid cancer (PTC). This adverse event has not been previously reported in thyroid cancer patients using dabrafenib. Case: A 61-year-old female with papillary thyroid cancer status post total thyroidectomy with pathology revealing right 7.6cm PTC with extrathyroidal extension and 13/72 metastatic lymph nodes. She received 100mCi of radioactive iodine (RAI). Ten months post-surgery, she underwent revision neck dissection with 3/36 nodes positive for metastatic disease and neck muscle invasion by PTC. Molecular testing demonstrated AKT1 and BRAFV600E mutations. Due to progressive neck and mediastinal tumors, recommendation was to proceed with systemic therapy. Initially started dabrafenib monotherapy; after 3 doses patient developed burning epigastric pain and fever. Examination revealed abdominal tenderness, elevated lipase at 2266 U/L (8-76U/L), mild hyperbilirubinemia and leukocytosis. CT abdomen/pelvis revealed peripancreatic fat stranding consistent with focal acute pancreatitis. No history of alcohol use. Dabrafenib was assessed to be culprit of pancreatitis; with immediate discontinuation of TKI and supportive management patient improved. At present patient is tolerating Lenvatinib therapy. BRAFV600E mutation occurs in 29-83% of thyroid cancers affecting growth, proliferation, survival, migration, and loss of tissue-specific differentiation via the intracellular MEK/ERK pathway1. RAI offers an important treatment modality for thyroid cancer patients, however patients with BRAFV600E are often poor responders or refractory to RAI1. Dabrafenib, a specific BRAFV600E tyrosine kinase inhibitor in combination with trametinib (a MEK inhibitor) is FDA approved for treatment BRAFV600E mutated anaplastic thyroid cancer; furthermore there is evidence on PTC responses including redifferentiation 2. Pancreatitis has been reported in <1% of dabrafenib treated patients as monotherapy and in combination with trametinib in unresectable or metastatic melanoma clinical trials. It was reported in 4% of patients in a NSCLC when used in combination with trametinib. Recurrent pancreatitis when dabrafenib was re-introduced at a lower dose has also been reported3. Furthermore, it was the cause of pancreatitis in a patient with metastatic melanoma 4 months into the treatment in combination with trametinib4. As this treatment option becomes increasingly utilized for metastatic or locally advanced anaplastic/papillary thyroid cancers, endocrinologists should be aware of the potential for dabrafenib induced pancreatitis during monotherapy use or in combination with trametinib.