Hazard Model for Brain Metastases After Prophylactic Cranial Irradiation in Local Disease Small Cell Lung Cancer

Abstract

Some patients with local-disease small cell lung cancer (LD-SCLC) still experience brain metastases (BM) even have received prophylactic cranial irradiation (PCI). We initiated this study to exploit risk factors for BM after PCI and develop harzard model to guide the clinical practice in LD-SCLC. LD-SCLC patients with PCI history from two institutions during 2003 and 2014 were retrospectively reviewed. BM free survival (BMFS), disease-free survival (DFS), extracranial disease-free survival (ECDFS), local recurrence-free survival (LRFS), and overall survival (OS) were estimated using Kaplan-Meier method. High risks and harzard model for BM were identified using univariate and multivariate Cox regression analyses. A total of 257 patients were eligible, among whom 47(18.3%) experienced BM at median follow-up of 34 months. In univariate analyses, performance status (PS) and thoracic radiotherapy schedule were associated with BM(P < 0.05). Multivariate analyses showed that worse PS (PS > 1),thoracic hyperfractionated accelerated radiotherapy (HART), longer start of any therapy to the end of radiotherapy(SER) were independent risks for BM and surgery was independent protective factor for BM (P < 0.05). Median LRFS, ECDFS, DFS and OS in the BM group were much shorter than the non-BM group(P < 0.05).In addition, elder than 60-yr, worse PS and PCI classification were independent risk factors for OS(P < 0.05). Surgery and thoracic radiotherapy biological effective dose (TRTBED) were independent protective factors for OS (P < 0.05). Worse PS, thoracic HART and longer SER were independent risks for BM after PCI in SCLC. Surgery decreased BM rate and improve OS. Prognosis was much worse in the BM group. Higher dose for PCI did not prolong BMFS but shortened OS. Further studies are needed to confirm our findings.