OBJECTIVES Occult primary non-small cell lung cancer (NSCLC) with mediastinal involvement is a known but rare clinical condition. Very limited retrospective data are available in the literature. Its prognosis and response to systemic chemotherapy have not been investigated with large scale data. MATERIALS AND METHODS Using National Cancer Database (NCDB), cases that had undergone radiation therapy without surgery for N2-3M0 NSCLC were selected. Demographics and survival data were compared between T0 and T1-4 groups. Survival analyses were conducted with Kaplan-Meier and log-rank tests. Cox proportional hazard models were used for univariate and multivariate analyses. RESULTS Between 2004 and 2016, 84,263 and 458 cases met criteria for unresectable stage III NSCLC with T1-4 and T0 stage, respectively. T0 status was associated with younger age, recent diagnosis (year 2010-2016), adenocarcinoma histology, N3 stage, and use of chemotherapy. Survival analysis demonstrated that those with T0 status had prolonged overall survival as compared to T1-4 counterparts in both overall and chemotherapy groups (p < 0.0001 for each). Five-year overall survival rates for T0 and T1-4 groups were 30.5% and 12.7% in all groups, and 33.6% and 14.6% in chemotherapy groups, respectively. Propensity score matching also demonstrated a statistically significant difference in overall survival (p < 0.0001). These findings are confirmed by independent analysis using Surveillance, Epidemiology, and End Results Program (SEER). CONCLUSION This large hospital-based study demonstrates the favorable prognosis for T0 status in the setting of unresectable stage III NSCLC. Researchers may consider it as distinct stage (e.g., stage IIC) for future studies.

中文翻译：

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T0 状态在不可切除的 III 期非小细胞肺癌总生存中的作用：NCDB 分析

目标 纵隔受累的隐匿性原发性非小细胞肺癌 (NSCLC) 是一种已知但罕见的临床疾病。文献中的回顾性数据非常有限。其预后和对全身化疗的反应尚未用大规模数据进行研究。材料和方法 使用国家癌症数据库（NCDB），选择接受放射治疗但未手术的 N2-3M0 NSCLC 病例。比较了 T0 和 T1-4 组的人口统计学和生存数据。使用 Kaplan-Meier 和对数秩检验进行生存分析。Cox 比例风险模型用于单变量和多变量分析。结果 2004 年至 2016 年间，分别有 84,263 和 458 例符合 T1-4 和 T0 期不可切除的 III 期 NSCLC 标准。T0 状态与年轻相关，最近的诊断（2010-2016 年）、腺癌组织学、N3 分期和化疗的使用。生存分析表明，与总体和化疗组中的 T1-4 对应者相比，具有 T0 状态的患者的总生存期延长（各自 p < 0.0001）。T0和T1-4组的5年总生存率各组分别为30.5%和12.7%，化疗组分别为33.6%和14.6%。倾向评分匹配也证明了总体生存率的统计学显着差异（p < 0.0001）。这些发现通过使用监测、流行病学和最终结果计划 (SEER) 的独立分析得到证实。结论 这项大型医院研究表明，在不可切除的 III 期 NSCLC 的情况下，T0 状态预后良好。