S5974 Unexpected Malignancy: Thyroid Carcinoma in a Pediatric Ulcerative Colitis Patient on Anti-TNF Therapy

Introduction: Pediatric inflammatory bowel disease (IBD) necessitates the use of biologic therapies, with tumor necrosis factor-alpha inhibitors (TNF-i) as the first line treatment to control inflammation and maintain remission. While TNF-i's have transformed IBD care, TNF-i treatment does not come without risk. Their immunosuppressant effects raise concerns about the risk of malignancy, such as lymphoproliferative cancers and non-melanoma skin cancers. Papillary thyroid cancer (PTC) is the most common type of thyroid cancer in adults and children. We present a case of an adolescent with IBD on a TNF-i, who developed PTC. Case Description/Methods: An 18-year-old female with an 11-year history of UC had an incidental thyroid nodule noted during a routine pediatric examination. At the time of her UC diagnosis, her initial therapy was balsalazide and 6-mercaptopurine. Due to persistent disease activity, around 2 years later, she was transitioned to a TNF-i, infliximab 10 mg/kg, and has remained on this therapy. Over the next year, her thyroid nodule progressively enlarged, and an ultrasound revealed a solid mass in the right lobe and isthmus, extending into the left lobe with the largest diameter measuring more than 5 cm. She was otherwise asymptomatic with no family history of thyroid disease. Fine needle aspiration of the nodule was consistent with PTC. She underwent total thyroidectomy and radioactive iodine (I-131) ablation. She required an additional cervical lymph node dissection 2 months later, but she has remained in remission since. Her UC remains in clinical remission on infliximab 10 mg/kg given every 6 weeks. Discussion: Biologic agents, like TNF-i’s, have revolutionized the management of IBD. However, they have been associated with increased risk of certain malignancies, although there is no current association with thyroid cancer. The most common risk factors for PTC includes ionizing radiation, family history of thyroid cancer, female sex, obesity, high dietary iodine intake, and certain environmental pollutants; with sex being the only risk factor in our patient. Due to the lack of association between PTC and TNF-i with IBD, we opted to keep her on this therapy. While there is still more to learn about the long-term effects of biologic agents, it is important to monitor for all potential outcomes in this population.