Several arguments are in favor of a therapeutic monitoring for the erlotinib, therefore, a pharmacokinetic (PK) has been prepared using data from the literature. This model must be validated at concentrations achieved in practice. This is a preliminary study before the implementation of a randomized trial confirming the therapeutic monitoring of erlotinib through this model.

Inclusion Criteria:

• All patients receiving treatment with erlotinib monotherapy for locally advanced or metastatic NSCLC either first line in patients with an activating mutation of the receptor EGF-R or patients with stable disease after 4 cycles of standard first-line chemotherapy with platinum or after failure of at least one prior chemotherapy regimen
• Age> 18 years
• Subject has signed an informed consent
• Treatment initiated for at least 7 days or dosage changed for at least 7 days

Exclusion Criteria:

• Contraindication to the use of drug
• Subject to exclusion period (as determined by a previous study or in progress)
• Inability to give informed information (subject in emergency situations, difficulties in understanding the subject, ...)
• Subject under judicial protection
• Subject under tutorship or curatorship
• Pregnancy (and woman of childbearing age without contraception)
• Breastfeeding

patients treated in the care departement of the hospital