Prognostic analysis and clinical characteristics of dual primary lung cancer: a population study based on surveillance, epidemiology, and end results (SEER) database

Background The peculiarity and the lack of clinical studies of dual primary lung cancer (DPLC) led to limited knowledge about its clinical characteristics and prognosis. This study performed a retrospective analysis to assess the prognostic factors and clinical characteristics of DPLC. Methods A total of 1419 DPLC patients from SEER were analyzed by univariate and multivariable Cox regression analyses. The independent prognostic factors were included to establish a nomogram. The accuracy and reliability of prognostic model were evaluated by C indexes, calibration plots, receiver operating characteristic (ROC) curves, decision curve analyses (DCA) and integrated discrimination improvement (IDI) scores. Chi-square test was used to assess the differences between DPLC and single primary lung cancer (SPLC) or synchronous DPLC (sDPLC) and metachronous DPLC (mDPLC). Results Cox regression analysis showed that age, sex, histological type, stage, lymph node (LN) metastasis, surgery, chemotherapy were independent prognostic factors, we included these factors to establish a nomogram. In the training cohort, the C index was 0.690, and the area under curves (AUC) of 3 and 5-year survival time were 0.720 and 0.723. The calibration plots in training cohort and validation cohort were in excellent agreement. DCA and IDI showed that the predictive effect of the novel prognostic model was better than the model based on 8th AJCC TNM system. Chi-square test indicated that DPLC and SPLC had statistical differences on pathological and clinical features. Conclusions The clinical and pathological characteristics of DPLC were different from the SPLC. The nomogram could provide accurate and individualized survival predictions for DPLC.