Pemetrexed in maintenance treatment of advanced non-squamous non-small-cell lung cancer

Pemetrexed, a multitargeting antifolate cytotoxic drug, plays a leading role in front-line chemotherapy for patients with advanced non-squamous non-small-cell lung cancer (NSCLC). Following its approval as second-line monotherapy for locally advanced or metastatic non-squamous NSCLC, pemetrexed has established itself as the first-line regimen in combination with cisplatin, and its powerful antitumor effects and less cumulative toxicities were then taken advantage of in the JMEN and PARAMOUNT trials, respectively, to pioneer a new treatment strategy of switch and continuation maintenance monotherapy. These developments have brought about a marked paradigm shift, and made pemetrexed indispensable in the treatment for non-squamous NSCLC. So far, only three drugs have been approved for maintenance therapy; pemetrexed both by switch and continuation maintenance, erlotinib by switch maintenance, and bevacizumab by continuation maintenance. Compared with observation alone after defined cycles of the first-line chemotherapy, subsequent pemetrexed maintenance therapy has provided significantly longer survival and infrequent severe adverse events. The cost-effectiveness of pemetrexed maintenance therapy is controversial, as well as the other two maintenance drugs, bevacizumab and erlotinib. The latest attractive attention is a combination maintenance therapy. We may have to consider epidermal growth factor receptor (EGFR) mutation status for selection of a combination pattern. A combination maintenance therapy of pemetrexed plus bevacizumab is potential for patients with wild-type EGFR status, while a EGFR tyrosine kinase inhibitor-containing combination is promising for patients with active EGFR mutation status. Pemetrexed will be a pivotal drug when a combination maintenance therapy is used in practice. For future maintenance therapy, we need to explore reliable predictive selection or exclusion markers that can predict who will really benefit from maintenance therapy.