Significance of targeted therapy and genetic alterations in EGFR, ALK, or KRAS on survival in patients with non-small cell lung cancer treated with radiotherapy for brain metastases

Background. We determined the impact of genetic alterations in EGFR, ALK, or KRAS on survival after radiotherapy for brain metastases in non-small cell lung cancer (NSCLC). Methods. Of 172 genotyped NSCLC patients treated with radiotherapy for brain metastases in 2005-2012, 54 had cancers with EGFR mutations, 12 had ALK rearrangements, 38 had KRAS mutations, and 68 were wild-type (WT). Overall survival (OS) was determined. Results. Median follow-up was 8.6 months. Median OS was 13.6 months for patients with EGFR mutations and 26.3 months for patients with ALK rearrangements, in contrast to 5.7 months for KRAS-mutant patients and 5.5 months for WT patients (P = .001). On multivariate analysis, adjusting for receipt of targeted therapy after cranial radiotherapy, ALK rearrangements were associated with improved OS (HR, 0.31; 95% CI, 0.13-0.74; P = .008). EGFR mutations were not significantly associated with improved OS on multivariate analysis (HR, 0.71; 95% CI, 0.37-1.38; P = .3). KRAS mutations were also not associated with improved OS (HR, 0.93; 95% CI, 0.59-1.47; P = .8). Receipt of targeted therapy after cranial radiotherapy was independently associated with improved OS (HR, 0.30; 95% CI, 0.17-0.54; P < .001). Receipt of chemotherapy after cranial radiotherapy, number of brain metastases, extra-cranial metastases, age, and performance status were also associated with OS. Conclusions. NSCLC patients with genetic alterations in ALK have improved survival outcomes after radiotherapy for brain metastases compared with EGFR, KRAS, or WT. Subsequent receipt of targeted therapy was associated with additional improvement in OS.