Pemetrexed plus cisplatin versus docetaxel plus cisplatin for stage IV lung adenocarcinoma based on propensity score matching.

The aim of this study was to compare the clinical efficacy of pemetrexed+cisplatin (PP) versus docetaxel+cisplatin (DP) for the treatment of stage IV lung adenocarcinoma. We retrospectively analyzed the clinical data of 147 patients with stage IV lung adenocarcinoma treated between January 2011 and December 2015, 100 of which were in the DP group whereas 47 were in the DP group. Main inclusion criteria were treatment-naive patients, first-line treatment with PP or DP with no molecular targeted therapy during treatment, 2-6 cycles of first-line chemotherapy with unknown status of epidermal growth factor receptor (EGFR) mutation, 18-75 years of age, and Karnofsky performance status score of at least 70. Prognostic factors for survival were identified by using univariate and multivariate analyses. Propensity score matching was performed to further adjust for confounding. A total of 47 pairs were successfully matched between the two groups. The median overall survival was 9.0 months in the DP group and 17.0 months in the PP group; the 1-year survival rate was 29.8 and 59.6%, respectively; the 2-year survival rate was 12.8 and 21.1%, respectively (χ=4.128, P=0.042); and median progression-free survival was 6.0 and 8.0 months, respectively (χ=4.839, P=0.028). Cox multivariate analysis showed that chemotherapy regimen and number of metastatic organs were independent factors for OS. The effect of the radiotherapy dose on the primary tumor on OS was close to statistically significant. The incidence of grade 3-4 neutropenia was more significantly reduced in the DP group than in the PP group after matching (61.7 vs. 27.7%, P=0.002), with no between-group difference for adverse effects on platelets or hemoglobin. For patients with stage IV lung adenocarcinoma and unknown EGFR mutation status, PP was more effective than DP in prolonging survival and had a less adverse effect on neutrophils.