Paradoxical response to osimertinib therapy in a patient with T790M-mutated lung adenocarcinoma

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.

EGFR T790M-Positive Lung Adenocarcinoma Metastases to the Pituitary Gland Causing Adrenal Insufficiency: A Case Report

A 64-year-old man, with history of micropapillary thyroid cancer and epidermal growth factor receptor-positive lung adenocarcinoma with no evidence of active disease for 3 years after chemotherapy and radiation on erlotinib, presented with fatigue, nausea, lack of appetite, and xeroderma. A screening magnetic resonance image of the patient's head demonstrated a new bilateral pituitary mass. Initial evaluation revealed low morning cortisol, and the patient was diagnosed with adrenal insufficiency. His symptoms rapidly improved with maintenance glucocorticoids. Soon thereafter, the patient developed an acute visual deficit secondary to enlargement of the pituitary mass, and biopsy revealed EGFR T790M positive metastatic lung adenocarcinoma. Hence, we present a rare case of metastatic lung adenocarcinoma to the pituitary causing secondary adrenal insufficiency.