This study was conducted to evaluate microRNAs (miRNAs) as biomarkers for use in predicting the efficacy of maintenance therapy with pemetrexed in patients with stage IIIb or IV lung adenocarcinoma and who had already received first-line treatment with pemetrexed plus platinum. Patients who were negative for epidermal growth factor receptor (EGFR) mutations or anaplastic lymphoma kinase (ALK) translocations were assigned to a pemetrexed group and an observation group. Patients in the pemetrexed group (n = 76) received maintenance treatment with pemetrexed (500 mg/m(2), once every 21 days) plus best supportive care. Patients in the observation group (n = 72) agreed to receive only best supportive care until disease progression. Blood samples were collected from all patients in both groups before treatment and were used to detect expression levels of various miRNAs in serum by the Reverse Transcription-Polymerase Chain Reaction (RT-PCR) method. The expression levels of miR-25, miR-145, and miR-210 were significantly different in the 2 groups of patients. Furthermore, the median progression-free survival (PFS) times for patients in the pemetrexed and observation groups were 4.5 and 2.9 months, respectively. The PFS times among patients in the pemetrexed group varied significantly and were related to patient expression levels of miR-25, miR-145, and miR-210, whereas patients in the observation group showed no differences in PFS time. Our data suggest miR-25, miR-145, and miR-210 as predictors for the efficacy of maintenance treatment with pemetrexed in lung adenocarcinoma patients who were negative for EGFR mutations or ALK translocations.
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