PURPOSE: To determine if it is preferable to extend chemotherapy beyond a standard number of cycles in patients receiving first-line chemotherapy for advanced non-small-cell lung cancer. METHODS: We searched biomedical literature databases and conference proceedings for randomized controlled trials (RCTs) comparing a defined number of cycles with continuation of the same chemotherapy until disease progression, a larger defined number of cycles of identical chemotherapy, and a defined number of cycles of identical initial chemotherapy followed by additional cycles of an alternative chemotherapy. Meta-analysis was performed using the fixed effect model. The primary outcome was overall survival (OS); secondary outcomes included progression-free survival (PFS), adverse events (AE), and health-related quality of life (HRQL). RESULTS: We found 13 RCTs including 3,027 patients. Extending chemotherapy improved PFS substantially (hazard ratio [HR], 0.75; 95% CI, 0.69 to 0.81; P < .00001) and OS modestly (HR, 0.92; 95% CI, 0.86 to 0.99; P = .03). Subgroup analysis revealed that effects on PFS were greater for trials extending chemotherapy with third-generation regimens rather than older regimens (HR, 0.70 interaction v 0.92 interaction; P = .003). Extending chemotherapy was associated with more frequent AE in all trials where it was reported and impaired HRQL in two of seven trials. CONCLUSION: Extending chemotherapy, particularly with a third-generation regimen, improved PFS substantially, but OS less so. Future trials should test extending treatment with more effective and/or better-tolerated agents.