The aims of this study are: (1) to assess the safety and activity of gemcitabine plus Alimta (pemetrexed) regimen (GA regimen) in patients with advanced NSCLC patients in the context of a randomized trial, and (2) to compare the GA with the paclitaxel plus gemcitabine (PG regimen) in terms of toxicity and QoL

Patients with stage IIIB or IV non-small cell lung cancer will be randomly allocated to receive: (a)PG regimen: paclitaxel 120 mg/sqm followed by gemcitabine 1,000 mg/sqm i.v. on days 1 & 8 q 3 weeks; (b)GA regimen: gemcitabine 1,250 mg/sqm i.v. on day 1 (plus folinic acid 350 μg daily orally and vitamin B12 1,000 μg i.m. q 9 weeks), pemetrexed (Alimta®) 500 mg/sqm i.v. on day 8 followed by gemcitabine 1,250 mg/sqm, q 3 weeks.

Inclusion Criteria:

1. Patients with histologically or cytologically confirmed locally advanced (stage IIIB) or metastatic (stage IV) NSCLC
2. No previous adjuvant or palliative chemotherapy
3. No previous radiotherapy
4. Presence of at least one unidimensionally measurable lesion (Appendix 2)
5. ECOG performance status of 0 or 1 (Appendix 3)
6. Charlson score ≤ 2 (Appendix 4)
7. Adequate bone marrow function (absolute neutrophil count ≥ 2 x 109/L, platelet count ≥ 100 x 109/L, and hemoglobin level ≥ 100 g/L), and adequate liver function (bilirubin level < two times the upper limit of normal, AST and/or ALT < three times the upper limit of normal, prothrombin time < 1.5 times control), and creatinine clearance ≥ 60 ml/min.
8. Absence of symptomatic CNS metastases (patients with cerebral metastases treated with brain irradiation may be included), severe cardiac arrhythmia or heart failure, second or third degree heart block or acute myocardial infarction within 4 months prior to study entry.
9. No major surgery or pleurodesis within 14 days prior to enrollment.
10. Life expectancy of at least 12 weeks.
11. No previous or concurrent malignancy, except inactive non-melanoma skin cancer, in situ carcinoma of the cervix, or other cancer if the patient has been disease-free for more than 5 years.
12. Written informed consent

Exclusion Criteria:

1. Any unstable systemic disease (including active infection, uncontrolled hypertension, unstable angina, congestive heart failure, serious cardiac arrhythmia requiring medication, hepatic, renal or metabolic disease).
2. Patients with clinically significant effusions.
3. Any other malignancies within 5 years that could affect therapy evaluation