title: Effectiveness of chemotherapy for advanced lung cancer in the elderly: instrumental variable and propensity analysis.
abstract: OBJECTIVE
  To compare the effectiveness of chemotherapy given to elderly patients in routine practice for stage IV non-small-cell lung cancer (NSCLC) with the efficacy observed in randomized trials.
  
  
  METHODS
  We used instrumental variable analysis (IVA) and propensity scores (PS) to simulate the conditions of a randomized trial in a retrospective cohort of patients over age 65 from the Survival, Epidemiology, and End Results (SEER) tumor registry. Geographic variation in chemotherapy use served as the instrument for the IVA analysis, and propensity scores were calculated with a logistic model based on patient disease and sociodemographic characteristics.
  
  
  RESULTS
  Among 6,232 elderly patients, the instrumental variable estimate indicated an increase in median survival of 33 days and an improvement in 1-year survival of 9% attributable to chemotherapy. In a Cox regression model, chemotherapy administration was associated with a hazard ratio of 0.81 (95% confidence interval, 0.76 to 0.85). When survival was analyzed separately within propensity score quintiles, the hazard ratios were all similar, ranging from 0.78 to 0.85. These results are comparable with those of a large meta-analysis, which found a hazard ratio of 0.87 in the subgroup of patients over age 65.
  
  
  CONCLUSIONS
  Chemotherapy for stage IV NSCLC seems to have effectiveness for elderly patients and those with comorbid conditions that is similar to the efficacy seen in randomized trials containing mostly younger, highly selected patients. All suitable patients should be given the opportunity to consider palliative chemotherapy for metastatic NSCLC.
authors.affiliation: Center for Outcomes and Policy Research, Dana-Farber Cancer Institute, Boston, MA 02115, USA. craig_earle@dfci.harvard.edu
authors.forename: C C
authors.initials: CC
authors.lastname: Earle
authors.forename: J S
authors.initials: JS
authors.lastname: Tsai
authors.forename: R D
authors.initials: RD
authors.lastname: Gelber
authors.forename: M C
authors.initials: MC
authors.lastname: Weinstein
authors.forename: P J
authors.initials: PJ
authors.lastname: Neumann
authors.forename: J C
authors.initials: JC
authors.lastname: Weeks
mesh_terms: D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy*; D015897:Comorbidity; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy*; D008297:Male; D011336:Probability; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012959:Socioeconomic Factors
chemical_list: D000970:Antineoplastic Agents