Background: EGFR-mutant NSCLC has an oncogene-addicted phenotype that confers sensitivity to EGFR TKIs. Prior data suggests EGFR addiction persists after development of TKI resistance, leading many clinicians to continue TKI along with chemotherapy (chemo); however, this strategy has not been formally evaluated. Methods: An institutional database was reviewed to identify patients (pts) with advanced NSCLC and acquired resistance to EGFR TKIs by Jackman criteria. Pts were included if they subsequently received chemo. Objective response rate (RR) to chemo/erlotinib or chemo alone was assessed by blinded radiographic review and compared by Fisher’s exact test and multivariable logistic regression. Progression-free survival (PFS) and overall survival (OS) from TKI failure (defined as chemo initiation date) were compared by log-rank test and multivariable Cox analysis. Results: 78 pts were eligible (34 chemo/erlotinib, 44 chemo alone). 70 pts (90%) had a documented EGFR mutation and were on TKI for a median of 15 months (range 4-51); in the 8 pts with unknown genotype the median duration on TKI was 11 months (range 5-16). Baseline characteristics were well balanced except more pts received erlotinib as initial TKI in the chemo/erlotinib group. RR was evaluable in 57 pts and was higher with chemo/erlotinib compared to chemo alone (41% vs 18%; OR 0.31, 95% CI 0.09, 1.04; p=0.08). RR adjusted for chemo regimen and time to TKI failure yielded OR 0.20 (95% CI 0.05, 0.78; p=0.02), favoring chemo/erlotinib. Median PFS was 4.4 months in the chemo/erlotinib group and 4.2 months in the chemo alone group (crude HR=0.84, 95% CI 0.52, 1.38; p=0.50; adjusted HR 0.79, 95% CI 0.48, 1.29; p=0.34). There was no significant difference in OS in the crude or adjusted analyses. Conclusions: This is the first study, to our knowledge, to show that continuation of an EGFR TKI with chemo compared to chemo alone significantly increases the RR in pts with advanced NSCLC and acquired TKI resistance, though we did not observe an impact on PFS or OS. Continued concurrent TKI may be a valuable strategy, particularly for pts with symptomatic progression, when a higher response rate may be beneficial. Further study is warranted.