Complete Resolution of Sellar Metastasis in a Patient With NSCLC Treated With Osimertinib

Non-small cell lung cancer with pituitary metastasis (NSCLC-PM) is a devastating disease; however, treatment is being revolutionized by a novel therapy targeting highly specific tumor signals, such as the mutation of epidermal growth factor receptors (EGFRs). Long-term management of hormonal defects in this population has become a unique neuroendocrine clinical challenge. We report the case of a 73-year-old female nonsmoker who was diagnosed with stage IV non-small cell lung cancer. The initial staging evaluation revealed a 7 × 11 × 21-mm sellar lesion abutting the optic chiasm and causing clinical hypopituitarism. The patient received three cycles of chemotherapy with carboplatin and pemetrexed, which was discontinued because of major cumulative side effects of myelosuppression and kidney disease. Eight months later, scans demonstrated evidence of disease progression. A repeated lung nodule biopsy revealed an EGFR exon 19 deletion mutation. EGFR-targeted therapy with osimertinib 80 mg daily was initiated. A complete resolution of the pituitary lesion was evident on a follow-up pituitary MRI 5 weeks later and was sustained 1 year after. However, the panhypopituitarism persisted. This is an illustrative case of NSCLC-PM with EGFR exon 19 deletion mutation, wherein osimertinib, a third-generation EGFR‒tyrosine kinase inhibitor, eradicated the sellar metastasis and prevented the need for radiotherapy. However, the neuroendocrine deficits persisted despite anatomic improvement.