OBJECTIVES: Lung cancer is the leading cause of cancer death in the United States. It is estimated that 60% of lung cancer patients are afflicted with cancer-cachexia and approximately 10% of these patients will die due to cancer-cachexia. We examined the impact of cachexia on survival among lung cancer elderly patients. METHODS: We conducted a retrospective study using SEER-Medicare data. Patients were included if diagnosed with first primary lung cancer between January 1, 2005 and December 31, 2010, at least 66 years of age, and continuously enrolled in Medicare Parts A and B in the 12 months prior to diagnosis. We identified cachexia in lung cancer patients using ICD-9 codes. Descriptive statistics were used to identify population characteristics. Propensity score (1:1 nearest neighbor) matching was performed between cachectic and non-cachectic lung cancer patients to compare survival.  RESULTS: We identified 84,518 lung cancer patients. Of these, 2,536 (3%) developed cachexia after lung cancer diagnosis. The most common comorbid conditions among cachectic and non-cachectic groups were chronic obstructive pulmonary disease (50% versus 45.62%), congestive heart failure (8.56% versus 13.38%), diabetes (7.41% versus 14.75%), peripheral vascular disease (3.82% versus 6.85%), and renal disease (3.63% versus 6.14%). Adjustment for immortal time bias resulted in a cohort of 3734 matched patients. Eighty-eight percent of patients in the cachectic group died during the follow-up period compared to 78% in the non-cachectic group. Median survival time among non-cachectic lung cancer patients was significantly longer than cachectic lung cancer patients (log-rank p<0.0001). Specifically, median survival in non-cachectic patients was 201 days compared to 92 days among cachectic patients. CONCLUSIONS: The occurrence of cachexia is independently associated with a significant decrease in survival among lung cancer elderly patients. The results of this study may be useful for identifying healthcare burden and planning treatment modalities for this population.