Background We reviewed patients treated for synchronous multifocal lung cancers (SMLCs) to analyze outcomes and evaluate valuable prognostic factors. Methods From January 2010 to June 2016, 3,031 patients underwent lung cancer resection at Jinling Hospital and Suzhou Hospital affiliated to Nanjing Medical University, and 164 (5.4%) had SMLC. The Kaplan-Meier method was used for survival analysis, and a multivariable Cox proportional hazards regression model was used for identification of independent survival predictors. Results The overall survival and progression-free survival rates with SMLC were 72.6% and 61.0%, respectively. A statistically significant difference existed for overall survival and progression-free survival between synchronous multiple primary lung cancer and intrapulmonary metastases according to Martini criteria. There was no statistical difference among the subgroups categorized by the TNM classification. Furthermore, small tumor size showed a benefit for overall survival and progression-free survival. Patients whose tumors were 0.8 cm or smaller had a 5-year survival rate of 100%. Tumor size, lymphatic metastases, and histologic differentiation were identified by univariate and multivariate regression analysis as independent survival predictors. Conclusions Survival of patients with SMLC is strongly correlated with the tumor size, differentiation, and lymphatic metastases but not with clinical TNM stage. The Martini criteria based on histologic subtyping has certain predictive value to survival. In comparison, tumor size is of greater value for prognosis. Both of the criteria above are much better than the TNM classification. The 5-year survival rate of 100% in patients with tumors sized 0.8 cm or smaller is extremely valuable for predicting survival after surgical resection.
