BACKGROUND In the eighth edition of the TNM classification of lung cancer, the M1b and M1c descriptors are newly defined by the number of extrathoracic metastases. To verify the prognostic value of these descriptors in Japan, we reclassified our cases and re-evaluated prognosis in M1b and M1c patients. METHODS All non-small cell lung cancer (NSCLC) patients with extrathoracic metastases who visited Saitama Medical Center from 2010 to 2016 were evaluated, divided according to the eighth edition of the TNM classification criteria into two groups (M1b, patients with single extrathoracic metastasis, and M1c, patients with multiple extrathoracic metastases), and followed up until December 31, 2017. Survival time analysis was performed using the Kaplan-Meier method, and between-group differences in overall survival time (OS) were evaluated by the log-rank test. RESULTS A total of 231 NSCLC patients were divided into 57 patients with M1b and 174 with M1c. Median OS was 15.2 months (95% confidence interval [CI]: 9.3-19.9) and 7.3 months (95% CI 5.7-10.7) for M1b and M1c, respectively, with no significant between-group difference (P = 0.239). However, after excluding patients with epidermal growth factor receptor (EGFR) mutation or echinoderm microtubule-associated protein-like 4 and anaplastic lymphoma kinase (EML4-ALK) fusion gene, median OS was 12.9 months (95% CI 7.2-19.9) for M1b and 5.4 months (95% CI 3.8-6.3) for M1c, respectively, showing a significant difference (P = 0.029). CONCLUSIONS The effect of therapy directed toward EGFR mutation or EML4-ALK fusion gene might obscure the significant prognostic difference between M1b and M1c.

中文翻译：

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根据第八次TNM分类对胸外转移灶数量的预后影响进行验证：日本的单机构回顾性研究。

背景技术在肺癌的TNM分类的第八版中，M1b和M1c的描述词是通过胸外转移的数目重新定义的。为了验证这些描述符在日本的预后价值，我们对病例进行了重新分类，并对M1b和M1c患者的预后进行了重新评估。方法对2010年至2016年访问visited玉医疗中心的所有非小细胞肺癌（NSCLC）胸外转移患者进行评估，根据TNM分类标准的第八版分为两组（M1b，单发胸外转移患者，和M1c，有多处胸腔外转移的患者），并随访至2017年12月31日。生存时间分析采用Kaplan-Meier方法进行，总体生存时间（OS）的组间差异通过对数秩检验进行评估。结果总共231例NSCLC患者分为57例M1b和174例M1c。M1b和M1c的中位OS分别为15.2个月（95％置信区间[CI]：9.3-19.9）和7.3个月（95％CI 5.7-10.7），组间差异无统计学意义（P = 0.239）。但是，排除具有表皮生长因子受体（EGFR）突变或棘皮动物微管相关蛋白样4和间变性淋巴瘤激酶（EML4-ALK）融合基因的患者后，M1b的中位OS为12.9个月（95％CI 7.2-19.9） M1c分别为5.4个月和5.4个月（95％CI 3.8-6.3），差异有统计学意义（P = 0.029）。