Strategies for Maintenance Therapies in Advanced Non Small Cell Lung Cancer

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.