Pemetrexed and Cisplatin as Treatment in Small Cell Lung Cancer

Inclusion Criteria: * Histologic or cytologic diagnosis of Small Cell Lung Cancer (SCLC). * Functional stage from 0 to 2 of the ECOG functional scale * No previous systemic chemotherapy, immunotherapy or biologic therapy for SCLC. * Previous bone marrow radiotherapy less than 25% is allowed. * There must be at least one measurable lesion that complies with the solid tumor response evaluation criteria. * Appropriate organic function. * Life expectancy estimated at 12 weeks minimum. * Females must be surgically sterile, postmenopausal or follow approved medical contraceptive methods during the treatment period and 6 months afterwards. Males must be surgically sterile or use a contraceptive method during the treatment period and during 6 months after treatment. * The patient must be compliant and located close to the trial area for appropriate follow-up. * The patient or his/her legal representative must sign an informed consent document. * Patients must be at least 18 years of age. Exclusion Criteria: * Having received treatment for the last 30 days with a drug that has not obtained regulatory approval. * Having participated in a previous pemetrexed trial. * Mixed histologic diagnosis of SCLC and NSCLC. * Concurrent illness. * Having an active infection. * Severe cardiac disease. * Having received recently or concurrently a vaccine against yellow fever. * Having suffered a previous malignant process other than SCLC. * Central nervous system (CNS) metastases require concurrent corticoid therapy. Treated and stable CNS metastases are allowed. * Clinically relevant fluid accumulation in the third space. * Significant weight loss (greater than or equal to 10%) within 6 weeks prior to trial inclusion. * Concurrent administration of any other anti-tumor treatment. * Severe renal failure. * Unable to discontinue administration of non-steroidal anti-inflammatory (NSAIDS) agents. * Inability or unwillingness to take folic acid and vitamin B12 supplements. * Inability to take corticoids.