Case series illustrating radiographic changes in leptomeningeal disease (LMD) in patients with epidermal growth factor receptor (EGFR) mutated non-small cell lung carcinoma (NSCLC) on treatment with tyrosine kinase inhibitors (TKIs).

EGFR is a transmembrane protein expressed by greater than 60% of NSCLCs. Clinically available tyrosine kinase inhibitors (TKIs) are effective in treating EGFR-mutant NSCLC.

Patient (pt) 1 had multifocal brain metastases (BM) treated with erlotinib, then osimertinib upon identification of EGFR T790M. They developed diplopia suggesting LMD in 10/2016. CSF cytology identified adenocarcinoma 2/2017, radiographic evidence was not noted until 10/2017.

Pt 2 had multifocal BM treated with erlotinib, transitioned to osimertinib due to EGFR T790M-mutated liver metastasis. They developed right hearing loss and facial weakness suggesting LMD 10/2016. Radiographic evidence of LMD was not apparent until 12/2016 with cytology positive 3/2017.

Pt 3 had a left midbrain BM treated with osimertinib and bevacizumab. Diplopia and confusion suggesting LMD developed 9/2018. They have no radiographic evidence of LMD to date, but cytology 9/2018 was read as atypical.

Pt 4 had been treated with multiple lines of therapy including erlotinib, followed by osimertinib. Cognitive difficulty and incontinence led to consideration of LMD 3/2018. Cytology was positive for adenocarcinoma 8/2018, with MRI brain evidence noted 9/2018.