An international multicenter clinical trial led by Belani (USA) comparing the clinical efficacy and safety of pemetrexed or placebo treatment given immediately after first-line chemotherapy for advanced lung cancer showed that patients treated with maintenance pemetrexed had an overall survival of 13.4 months compared to 10.6 months in the placebo group (p=0.012). This means that the use of pemetrexed as maintenance therapy reduces the risk of death by 21%. As demonstrated in the first-line treatment study, pemetrexed was the most effective in maintenance therapy for lung adenocarcinoma, with a median survival of 15.5 months (P=0.002) but not different from placebo for squamous lung cancer, with a median survival of 9.9 months (P=0.67). It is noteworthy that pemetrexed maintenance therapy has few serious toxicities, with only a 3% incidence of grade 3/4 granulocytopenia and anemia and a 5% incidence of fatigue, making it a chemotherapeutic agent whose toxicity is fully tolerated by patients.