Patterns of recurrence after intracranial stereotactic radiosurgery for brain-only metastases from non-small cell lung cancer and the impact of upfront thoracic therapy with synchronous presentation

Background: We characterized long-term organ-specific patterns of recurrence, time to progression (TTP) and overall survival (OS) in patients with non-small cell lung cancer (NSCLC) with brain-only metastases treated with single-fraction stereotactic radiosurgery (SRS) and analyzed the impact of upfront thoracic therapy (UTT) in those with synchronous presentation of primary NSCLC and brain metastases. Methods: The clinical records of 137 patients with brain metastases from NSCLC treated with intracranial SRS, and no other metastatic sites, were retrospectively reviewed. Patients with available follow-up imaging (n=124) were analyzed for patterns of recurrence; all were analyzed for OS. Results: The majority of first distant recurrences were in brain and thoracic sites, while extra-thoracic sites were relatively uncommon. After median follow-up of 16.0 months, 24.8% did not develop recurrence outside of brain and/or thoracic sites and 43.5% were free of distant extracranial recurrence. Whole brain radiotherapy (WBRT) and UTT, but not systemic therapy, altered patterns of recurrence and intracranial or extracranial TTP. Multivariable analysis revealed UTT, but not systemic therapy or WBRT, was associated with more favorable OS [hazard ratio (HR) 0.515, P=0.029] among 88 patients with synchronous presentation. Within the subgroup of thoracic stage III patients (n=69), those treated with UTT experienced remarkable median extracranial TTP and OS of 19.3 and 22.7 months, respectively. Conclusions: First and cumulative recurrences in patients treated with intracranial SRS for NSCLC metastases limited to brain are most often in the brain and thorax. Long-term survival is possible, regardless of thoracic stage, and is dependent on UTT among other factors.