The objective of this trial is to improve the duration of control disease for PS 0-1 patients who are not progressing on first-line cisplatin-gemcitabine chemotherapy. Standard therapy is for these patients to stop first-line chemotherapy after 4 to 6 cycles and to begin a second-line chemotherapy when progression of disease is occurring. Two approaches will be experimented in this trial in attempt to prolong progression free survival :

• Maintenance chemotherapy with single-agent gemcitabine continued till disease progression or toxicity.
• Sequential treatment with erlotinib immediately given after the end of first-line chemotherapy.

Inclusion Criteria:

• Histologically documented NSCLC (tumor tissue samples will be provided to look for assessment of EGFR status with CISH, immunochemistry and mutations) : adenocarcinoma, squamous cell carcinoma, large cell carcinoma. A cytological documentation of NSCLC is accepted.
• Stage IV disease or metastatic relapse in not previously irradiated areas of a NSCLC previously treated with surgery or radiation therapy (with a histologically documented proof of relapse) or stage III B with documented pleural involvement.
• Measurable disease according to the RECIST criteria.
• Prior radiotherapy authorized except for irradiation concerning measurable disease.
• Age >18 and < 70 years.
• PS < 2.
• Normal hepatic function : serum bilirubin < 1.5 ULN, SGOT (ASAT) and SGPT (ALAT) < 2,5 ULN ; in presence of liver metastases, SGOT and SGPT must be < 5 x ULN.
• Creatinine clearance > 60 mL/min.
• Granulocyte count > 1,5 giga/L, platelet count > 100 giga/L.
• Life expectancy > 12 weeks.
• Written (signed) informed consent for use of tumors samples.
• Written (signed) informed consent to participate in the sudy.

Exclusion Criteria:

• Small cell lung cancer, bronchiolo-alveolar carcinoma, neuro-endocrine carcinoma.
• PS > 1.
• Prior chemotherapy other than cisplatin-gemcitabine.
• Prior therapy with EGFR inhibitor (e.g. monoclonal antibody).
• No concomitant therapy with phenytoin, carbamazepine, rifampicine or phenobarbital.
• Concomitant radiotherapy except for localized bone irradiation.
• Symptomatic brain metastases.
• Superior vena cava syndrome.
• Any unstable systemic disease : significant cardiovascular disease including myocardial infarction within the previous year, active infection, significant hepatic or renal disease.
• Pre-existing interstitial lung disease.
• Any inflammatory changes of the surface of the eyes.
• Psychiatric disease with inability to understand the study or to comply with follow-up procedures.
• Grade > or = 2 peripheral neuropathy.
• Any other malignancies within 5 years (except for treated carcinoma in situ of the cervix or basal cell skin cancer).
• Pregnant or lactating women ; patients with reproductive potential must use effective contraception.
• Inability to comply with follow-up procedures.