Objective  To analyze the clinicopathological characteristics and prognostic factors of multifocal lung cancer (MFLC) patients.

  Methods  From January 2012 to January 2018, 187 MFLC patients whose largest lesion diameter was ≤4 cm and without lymphatic involvement or systemic metastases, were retrospectively reviewed. All the patients received surgical treatment. The Kaplan-Meier method was used for survival analysis, and a multivariable Cox proportional hazards regression model was used to assess the independent prognostic factors.

  Results  Among 187 cases, 173 were simultaneous MFLC (SMFLC) and 14 were metachronous MFLC (MMFLC). The 5-year disease-free survival (DFS) and overall survival (OS) rates of this group MFLC patients were 63.5% and 89.1%, respectively. In the SMFLC group, according to the American College of Chest Physicians (ACCP) guidelines (3^rd edition), 133 patients were defined as synchronous multiple primary lung cancer (SMPLC) while 40 patients had intrapulmonary metastases, there was no statistical difference in DFS between the two subgroups (P=0.531). EGFR mutation status (same mutations, different mutations, all wild-type) had no statistically significant effect on DFS of SMFLC (P=0.388). Univariate and multivariate regression analysis revealed that radiographic feature of solid nodules (hazard ratio (HR)=7.4, P=0.008) and MMFLC (HR=5.6, P=0.001) were independent risk factors for poor prognosis.

  Conclusion  MFLC can achieve a favorable prognosis with early surgical treatment. Tumor density and metachronous lesions are two important prognostic predictors.