• - To estimate the clinical benefit rate (CR, PR, SD) of pemetrexed in two patient populations with small cell lung cancer: chemosensitive and chemoresistant relapsed independently. [ Time Frame: 12 months ] [ Designated as safety issue: No ]
  

• To determine the toxicity of pemetrexed; To estimate the time to disease progression; To estimate overall survival [ Time Frame: 12 months ] [ Designated as safety issue: Yes ]
  

OUTLINE: This is a multi-center study.

• Pemetrexed 500 mg/m2 i.v. q 3 wks

All patients will also receive folic acid 350-1000 mcg. po once daily beginning approximately 1 week prior to the first dose of pemetrexed and continuing until completion of pemetrexed, Vitamin B12 1000 mcg. IM every 9 weeks beginning approximately 1 week prior to the first dose of pemetrexed and continuing until completion of pemetrexed, and dexamethasone 4 mg po bid the day before, the day of, and the day following each treatment with pemetrexed

Chest x-ray will be performed prior to each cycle (if other disease assessment by imaging is not performed) in order to ensure patients are not rapidly progressing.

Cycles are repeated every 3 weeks for up to 6 cycles or PD or intolerable side effects.

Performance Status: ECOG 0, 1, or 2

Life Expectancy: Not specified

Hematopoietic:

• WBC > 3000/mm3
• ANC > 1500/mm3
• Platelet count > 100,000/mm3
• Hemoglobin > 8 g/dL

Hepatic:

• Bilirubin < 1.0 X upper limit of normal
• Aspartate aminotransferase (AST, SGOT) < 2.5 x upper limit of normal. AST may be < 5 x upper limit of normal for patients with liver metastasis

Renal:

• Creatinine clearance of > 45 ml/ min (by Cockcroft-Gault)

Cardiovascular:

• No unstable or uncompensated cardiovascular conditions

Pulmonary:

• No unstable or uncompensated respiratory conditions