Managing Brain Metastases in HER2-Mutant NSCLC: CNS Activity and Integration with Local Therapy

This episode examines second-line therapy selection when brain metastases are present in HER2-mutant non-small cell lung cancer. Sandra presents with two small enhancing lesions—a 12-mm left frontal and 8-mm right parietal lesion—accompanied by morning headaches and word-finding difficulty, without significant surrounding edema or midline shift. Dr. Doroshow frames available post-first-line HER2-directed options: two tyrosine kinase inhibitors (zongertinib and sevabertinib) and one antibody-drug conjugate, trastuzumab deruxtecan (T-DXd). She notes intracranial activity data for sevabertinib are not yet available, while a small subset of patients with HER2-mutant non-small cell lung cancer and brain metastases treated with zongertinib demonstrated approximately 44% intracranial response rate. Trastuzumab deruxtecan also has documented central nervous system activity, though reported data combine treated and untreated brain metastases.

Dr. Doroshow contrasts these modest response rates with more robust central nervous system activity seen with agents like osimertinib in EGFR-mutant disease or lorlatinib in ALK-positive tumors, emphasizing HER2-directed therapies may provide 40-50% intracranial activity but don't approach deeper penetration of other targeted agents. For symptomatic patients like Sandra with bothersome headaches and neurologic symptoms, she would not wait to address brain disease. The discussion turns to integrating stereotactic radiosurgery with systemic HER2-targeted treatment. Dr. Doroshow emphasizes decisions depend on lesion size, symptom burden, edema presence, and midline shift. For smaller symptomatic lesions like Sandra's, stereotactic radiosurgery offers an attractive option: It is quick, typically single-fraction, and well-tolerated.

In the next episode, "Second-Line Treatment Selection Among HER2-Directed Therapies: Comparing Efficacy, Safety, and Patient Factors," Dr. Doroshow walks through how to choose among zongertinib, sevabertinib, and T-DXd based on patient-specific considerations.