A comparison of combination chemotherapy of sildenafil plus carboplatin and weekly taxol with carboplatin and weekly taxol in patients with previously untreated advanced non-small cell lung cancer. The study hypothesis is that sildenafil may improve the distribution and efficacy of cytotoxic anticancer agents.

Sildenafil is one of selective phosphodiesterase type 5 inhibitors. It is used to block the degradative action of phosphodiesterase type 5 on cyclic GMP in the smooth muscle cells lining the blood vessels, which leads to smooth muscle relaxation in blood vessels and increases blood flow. Because phosphodiesterase type 5 is also present in the arterial wall smooth muscle within the lungs, phosphodiesterase type 5 inhibitors is also used for the treatment of pulmonary hypertension.

Inclusion Criteria:

• Diagnosis of histologically confirmed stage IIIB or IV non-small cell lung cancer
• Good performance status (ECOG 0-1)
• No previous treatment
• Adequate bone marrow, liver and renal functions
• Must be able to swallow tablets
• Provided written informed consent

Exclusion Criteria:

• Severe complications or a concomitant malignancy
• Contraindicated sildenafil, carboplatin or taxol
• Inappropriate patients for entry to this study, judged by the physicians