Osimertinib-induced rapid regression of large metastatic tumor to the pituitary in a patient with lung adenocarcinoma

BACKGROUND: Metastatic nonsmall cell lung cancer (NSCLC) to the pituitary (NSCLC-PitM) is rare and often presents with visual field deficits. Surgical resection for the decompression of the optic apparatus has been the treatment of choice in such cases. Osimertinib is a third-generation tyrosine kinase inhibitor (TKI) approved for the treatment of patients with NSCLC with an epithelial growth factor receptor (EGFR) mutation though its role in the treatment of NSCLC-PitM that remains unclear. We present a case of NSCLC-PitM with optic chiasm compression and visual deficits that were successfully treated with osimertinib alone without surgical intervention. CASE DESCRIPTION: A 43-year-old male presented with pleuritic chest pain, fatigue, and visual deficits found to have NSCLC and a sellar mass with suprasellar extension and optic chiasm compression. Visual field testing demonstrated associated visual field deficits. Molecular testing was positive for EGFR exon 19 deletion. The patient was started on osimertinib with complete resolution of pituitary lesion and visual deficits at 4 weeks. CONCLUSION: Osimertinib is a third-generation EGFR-TKI that has demonstrated promising results among patients with metastatic EGFR-mutated NSCLC. While surgery is the mainstay of treatment in patients with a sellar mass, optic compression, and visual deficits, those with EGFR-mutated NSCLC-PitM may benefit from early initiation of such systemic therapies, rather than surgical intervention, with good ophthalmologic results.