Impact of non-small cell lung cancer histology on survival predicted from the graded prognostic assessment for patients with brain metastases

Abstract

IntroductionThe Graded Prognostic Assessment (GPA) provides prognostic classification for patients with brain metastases (BM), based on Radiation Therapy Oncology Group (RTOG) data. Recent evidence suggests differential response and outcomes to chemotherapy for different non-small cell lung cancer (NSCLC) histologies. Using a large BM patient database, we assessed the impact of histologic subtypes on survival stratified by the GPA. MethodsFrom an IRB-approved database, we analyzed 780 patients with NSCLC BM treated from 1982 to 2004. GPA classification variables included age, KPS, number of BM, and presence of extracranial disease. Histology was identified for each patient. Median survival time (MST) based on GPA class and histology were calculated using Kaplan–Meier analysis. The log rank test was used to determine statistical differences. ResultsMST, in months, by histology were: adenocarcinoma (AC) 6.2 (n=464), large cell (LC) 4.1 (n=98), squamous (SQ) 4.2 (n=108) (p=0.0549). For GPA 3.5–4.0, MSTs did not differ significantly by histology. Differences in MST by histology were noted for GPA 3.0 (p=0.04), GPA 1.5–2.5 (p=0.01), and GPA 0–1.0 (p=0.02). For all patients with brain metastases BM from NSCLC, MSTs by GPA score were: GPA 3.5–4.0, 12.6; GPA 3.0, 10.2; GPA 1.5–2.5, 5.8; and GPA 0–1.0, 2.7. ConclusionsAdenocarcinoma showed a statistically significant higher MST than other histologies of NSCLC for patients with GPA 0–3.0. Using histology as a prognostic factor for BM from NSCLC warrants further investigation. Our cohort of NSCLC BM patients validates the GPA, with MST comparable to that of published data.