A peculiar case of the abscopal effect: radioactive iodine therapy incidentally palliating marginal zone lymphoma

The abscopal effect is an extremely rare phenomenon occurring when irradiation or treatment of a primary tumor burden not only results in debulking of the targeted site but also reduces tumor size at distant sites from the intended treatment area. We present the abscopal effect occurring in a patient with low-grade marginal zone lymphoma who subsequently received radioactive iodine therapy for papillary thyroid carcinoma. She was 67 years old when a routine complete blood count at her primary care physician's office yielded a persistent leukocytosis of 14,500/μL with lymphocytosis of 9,870/μL. Immunophenotyping and fluorescence in situ hybridization (FISH) analysis confirmed low-grade marginal zone lymphoma. Over eight years, her peak leukocyte and lymphocyte counts were 24,100/μL and 18,100/μL, respectively. Subsequently, she was diagnosed with papillary thyroid carcinoma after presenting with a new complaint of dysphagia. A total thyroidectomy was performed, followed by 172.1 millicuries of oral I-131 sodium iodine radioactive ablation therapy. Following treatment, her leukocyte and lymphocyte counts were 3,100/μL and 1,100/μL, respectively. Over the next four years, her leukocyte and lymphocyte counts remained within normal limits and she remained symptom free. To our knowledge, there has never been a published report describing the use of radioactive iodine causing abscopal effect benefits for patients with underlying lymphoproliferative diseases.