Carcinomatosis under control by osimertinib in EGFR and TP53 mutated lung adenocarcinoma

Introduction: Approximately 25%-30% of patients with non-small cell lung cancer (NSCLC) develop central nervous system (CNS) metastases during the course of the disease; this percentage is higher in patients with epidermal growth factor receptor (EGFR) mutations. Leptomeningeal metastases, infrequent in the advanced setting, have a particularly dismal prognosis. Osimertinib, a third-generation EGFR inhibitor, can provide effective and durable response in this setting. Case Description: We present a 62-year-old man with progressive vomiting, headache, short-term memory impairment, and left lower limb hyposthenia. Computed tomography (CT) showed bilateral lung nodules, multiple lymphadenopathies, liver and bone metastases, and CNS and leptomeningeal dissemination, including multiple parenchymal nodules located at supra- and infratentorial brain. Bone needle biopsy documented TTF1+ lung adenocarcinoma. Whole brain radiotherapy (WBRT) and symptomatic treatments were started. Next-generation sequencing reported deletion of exon 19 of EGFR and mutation 8 of TP53. Osimertinib 80 mg was promptly started and WBRT interrupted. Some days after the patient experienced repetitive seizures and neurologic worsening, antiepileptic drugs and dexamethasone were implemented, with gradual improvement. Radiologic evaluation, including brain MRI and thorax-abdominal CT, showed partial response on CNS as well as extracranial sites, which was sustained. Conclusions: First-line treatment with osimertinib can be safe and effective in EGFR-mutated NSCLC even in presence of multiple negative predictive factors (poor Performance Status, diffuse leptomeningeal involvement, TP53 comutation), suggesting that deferring local treatments can be feasible in this setting, allowing the patient to maintain a good quality of life.