In France, lung cancer is responsible for more than 30000 each year. Progress was made in treatment of lung cancer in the last five years due to targeted therapies and to strategical evolutions consisting in a best adjustment of treatments. Maintenance strategies is one of this strategical evolution. It is based on maintaining continuous therapeutical pression in order to preserve the therapeutical benefit obtained by the first line (induction chemotherapy). Several clinical trials showed that maintenance strategies increase the duration of controlled disease.

There is two types of maintenance strategies:

• Continuous maintenance : prolongation of the treatment initially associated with platin until progression
• Switch maintenance : introduction of a new treatment after the end of induction chemotherapy

The aim of this study is to compare two maintenance strategies

• A continuous maintenance by pemetrexed
• A switch maintenance or a continuous maintenance according to the response of induction chemotherapy.

Inclusion Criteria:

• Non-squamous NSCLC histologically or cytologically confirmed
• Stage IV with a cytologically or histologically confirmation for an unique metastasis
• No EGFR activating mutation or indeterminate EGFR mutational status
• At least one measurable lesion
• Age between 18 and 70
• PS 0 or 1

Exclusion Criteria:

• squamous cell lung cancer, small cell lung cancer , neuroendocrine cell lung cancer
• Knowledge of ALK gene rearrangement
• Symptomatic central nervous system metastases or requiring immediate cerebral radiotherapy
• Superior venous cave syndrome except if treated by implantation of a prosthesis
• Previous anti-tumoral treatment
• Concomitant radiotherapy