癌症是台灣死因之首，其中肺癌又是死亡率最高的癌症，如何有效降低肺癌死亡率也隨之成為重要的研究議題。而社會經濟地位的差異往往影響患者得到肺癌的機率、發現肺癌的期別與存活的時間，找出社會經濟因子與肺癌存活時間的關係與其潛在機制，將有助於提升醫療決策的品質與改善醫療資源的分配。本研究以美國國家癌症研究所的The Surveillance, Epidemiology, and End Results（SEER）資料庫為分析資料，透過敘述統計、存活分析、中介分析探討社經因子與肺癌的關係與期別所造成的中介效果。本研究利用基於反事實的中介效果分析發現雖然社經地位高的病患生存率較高、風險比較低，但亦實證其間的關係有一部分可以被歸因為期別所造成的中介效果，表示透過初期檢測的介入將有助於提高存活。

Cancer is the main cause of death in Taiwan. Among all cancers, lung cancer has the highest mortality in Taiwan. Because cancer patients of lower socioeconomic status tend to have poorer survival, conducting a mediation analysis of the relationship between socioeconomic factors and survival of lung cancer may determine whether an intervention should be in the area of early detection or in the area of treatment, and thus can lead to a better allocation of medical resources. In this study, we analyze the database from The Surveillance, Epidemiology, and End Results (SEER) project of the National Cancer Institute of the United State by using survival analysis techniques. In particular, a novel medication analysis based on the counterfactual variables was implemented to investigate the mediation effect of the cancer stage on the relationship between socioeconomic factors and lung cancer survival. Results show that the cancer stage at presentation explains a significant portion of socioeconomic differences in lung cancer survival. This finding suggests that a policy which can lead to an intervention in the area of early detection should be considered.

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