Outcome of gamma knife radiosurgery for metastatic brain tumors derived from non-small cell lung cancer

The purpose of this study was to analyze outcomes in patients treated with gamma knife radiosurgery (GKS) for brain metastases from non-small cell lung cancer (NSCLC). We retrospectively reviewed the medical records of 817 patients who underwent GKS for brain metastases from NSCLC between January 2002 and December 2012. A total of 1363 GKS procedures were performed for 2970 lesions. The median overall survival time from the initial GKS was 13 months and the salvage treatment-free survival from the first GKS was 6.5 months. Younger age (≤65 years), female sex, better RPA class, higher DS-GPA score, adenocarcinoma, synchronous onset, and lower integrated value of the “numbers and cumulative volume of tumors” were associated with better outcomes. Among the 601 patients with an available follow up image, the pattern of the first progression after initial GKS was the development of new lesions in 356 patients (59.2 %), regrowth of treated lesions in 106 patients (17.6 %), and leptomeningeal seeding (LMS) in 51 patients (8.5 %). Among the deceased, the last MRI performed prior to death was evaluated in 409 patients and showed progression in 263 patients (64.3 %), despite multiple salvage treatments. LMS was identified in 63 patients (15.4 %); a rate much higher than the incidence at first progression. Intracranial tumor burden, defined as the integrated value of the “number of the lesions and cumulative tumor volume”, is a new prognostic factor of greater significance than tumor volume or number alone when analyzed as separate factors. Although the cause of death was not progression of brain lesions in the majority of patients, the brain lesions tended to have been persistently progressive in most patients, despite repeated salvage treatment. LMS is an important pattern of treatment failure, in addition to local progression or development of new lesions, particularly in the terminal phase of the disease.