Purpose: An American Society of Clinical Oncology (ASCO) focused update updates a single recommendation (or subset of recommendations) in advance of a regularly scheduled guideline update. This document updates one recommendation of the ASCO Guideline Update on Chemotherapy for Stage IV Non-Small-Cell Lung Cancer (NSCLC) regarding switch maintenance chemotherapy. Clinical Context: Recent results from phase III clinical trials have demonstrated that in patients with stage IV NSCLC who have received four cycles of first-line chemotherapy and whose disease has not progressed, an immediate switch to alternative, single-agent chemotherapy can extend progression-free survival and, in some cases, overall survival. Because of limitations in the data, delayed treatment with a second-line agent after disease progression is also acceptable. Recent Data: Seven randomized controlled trials of carboxyaminoimidazole, docetaxel, erlotinib, gefitinib, gemcitabine, and pemetrexed have evaluated outcomes in patients who received an immediate, non-cross resistant alternative therapy (switch maintenance) after first-line therapy. Recommendation: In patients with stage IV NSCLC, first-line cytotoxic chemotherapy should be stopped at disease progression or after four cycles in patients whose disease is stable but not responding to treatment. Two-drug cytotoxic combinations should be administered for no more than six cycles. For those with stable disease or response after four cycles, immediate treatment with an alternative, single-agent chemotherapy such as pemetrexed in patients with nonsquamous histology, docetaxel in unselected patients, or erlotinib in unselected patients may be considered. Limitations of this data are such that a break from cytotoxic chemotherapy after a fixed course is also acceptable, with initiation of second-line chemotherapy at disease progression. © 2011 by American Society of Clinical Oncology.