Purpose: KRAS mutation has been associated with enhanced dependency on the folate metabolism in preclinical studies. However, whether KRAS mutation correlates to increased sensitivity to pemetrexed in patients with advanced NSCLC is unknown.
Methods: Patients with advanced non-squamous NSCLC who had a documented EGFR and ALK WT genotype with simultaneous KRAS mutation assessment were evaluated for clinical outcome to pemetrexed- and non-pemetrexed-based first-line platinum doublet according to KRAS mutation status.
Results: Of 356 patients identified, 138 harbored a KRAS mutation. Among KRAS-mutant NSCLCs, those treated with platinum/pemetrexed (81/138) had significantly lower ORR (30.9% versus 47.4%, P = 0.05), DCR (51.8% versus 71.9%, P = 0.02) and shorter median progression-free survival [mPFS 4.1 versus 7.1 months, HR 1.48 (95% CI 1.03-2.12), P = 0.03] and median overall survival [mOS 9.7 versus 26.9 months, HR 1.93 (95% CI 1.27-2.94), P = 0.002] compared to those who received a non-pemetrexed-based platinum doublet (57/138). No difference in ORR, DCR, mPFS and mOS was observed between KRAS WT patients who received a pemetrexed-based (124/218) versus non-pemetrexed base platinum doublets (94/218). After adjusting for performance status, age and the presence of brain metastasis at baseline, treatment with pemetrexed-based platinum doublet was associated with an increased risk of death [HR 2.27 (95% CI 1.12-4.63), P = 0.02] among KRAS-mutant patients in multivariate analysis.
Conclusion: Patients with KRAS-mutant lung adenocarcinoma have a poorer outcome on pemetrexed-based first-line chemotherapy. Whether KRAS-mutant NSCLCs should be excluded from pemetrexed-containing regimens should be assessed prospectively.
Keywords: KRAS; Lung adenocarcinoma; Pemetrexed.