Targeted (and chemotherapeutic) agents as maintenance treatment in patients with metastatic non-small-cell lung cancer: current status and future challenges.

Maintenance treatment has been intensively investigated in the field of advanced/metastatic non-small lung cancer in order to improve outcomes in this devastating disease. Two different approaches have been evaluated; the so-called continuation maintenance when the maintenance agent was part of initial therapy and is continued in the absence of disease progression ("maintained") or switch maintenance when a third agent is initiated after a defined number of cycles chemotherapy in the absence of disease progression. Several phase III trials with both chemotherapeutic and targeted agents have demonstrated either PFS prolongation (continuation maintenance) or both PFS and OS benefit (switch maintenance). Currently, erlotinib and pemetrexed are registered as maintenance treatment in patients with NSCLC not progressing after four cycles of standard platinum-based doublet chemotherapy. However, the development of maintenance treatment has raised a series of questions such as the role of treatment-free intervals, the timing of second-line treatment, selection of patients for maintenance treatment and selection of the most proper agent, and trial design issues such as optimal end-points. The purpose of this paper is to present and discuss the current trials investigating the main treatment paradigms and argue on the above mentioned questions.