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Abstract Background There are some changes in the new 9th edition Tumor-Node-Metastases (TNM) staging system for lung cancer, including subdividing M1c into M1c1 and M1c2 stage. The aim of this study was to assess the prognostic performance of the updated classification system and try to provide some real-world application data among advanced lung adenocarcinoma patients with bone metastases. Methods Advanced lung adenocarcinoma patients in M1c stage with bone metastases who receiving first-line first-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) and T790M-guided osimertinib as the second-line therapy were retrospectively screened from December 2016 to December 2021. A total of 126 patients were enrolled in this study. 62 patients and 64 patients were subdivided into M1c1 and M1c2 groups according to the 9th edition of TNM staging system.The first-line real-world progression-free survival (1LrwPFS), the second-line real-world progression-free survival (2LrwPFS), post-progression survival (PPS) and real-world overall survival (rwOS) were analyzed. Results The overall median rwOS was 40.1 months (95% CI 35.996–44.204). 1LrwPFS was 13.9 months (95% CI 12.653–15.147) and 2LrwPFS was 14.5 months (95% CI 11.665–17.335) for all patients.Patients in M1c2 stage was inferior to M1c1 stage patients in rwOS (35.2 months vs. 42.9 months, HR = 0.512, P = 0.005). 2LrwPFS was moderately correlated with rwOS (r = 0.621, R2 = 0.568, P = 0.000). Multivariate analysis showed performance status (PS) score ≥ 2 and TP53 alteration positive were independent prognostic factors of worse rwOS. Conclusions More refined stratification of M1c according to the 9th edition of TNM staging system is conducive to the judgment of prognosis and the implementation of precision medicine for patients.