Combination of Gemcitabine and Imatinib Mesylate in Pemetrexed-pretreated Patients With Pleural Mesothelioma

Inclusion Criteria: 1. Age of \> 18 years. 2. Histologically proven malignant mesothelioma of the pleura or of the peritoneum, expressing PDGFR-beta and/or C-kit by immunohistochemistry. 3. Locally advanced disease, unsuitable for curative surgical resection, or metastatic disease. 4. Confirmed progression of the disease according to modified RECIST-criteria, documented after a pemetrexed-based chemotherapy. 5. Eastern Cooperative Oncology group (ECOG) Performance Status of 0, 1 or 2. 6. Life expectancy of at least 3 months. 7. Written informed consent. Exclusion Criteria: 1. Co-existing tumors of different histologic origin, except non melanomatous localized skin cancer and/or in situ cervical carcinoma. 2. A history of earlier tumors of different histologic origin being in complete remission for less than 5 years. 3. Unresolved toxicity from prior antitumor treatment(s). 4. Primary peritoneal mesothelioma. 5. Any of the following abnormal baseline hematological values: * Hb \< 9 g/dL * White blood count (WBC) \< 3 x 109/L * Neutrophils \< 1.5 x 109/L * Platelets \< 100 x 109/L * Serum bilirubin \> 2.5 mg/dL * Alanine transaminase (ALAT) and Aspartate transaminase (ASAT) \> 3 x upper normal limit (UNL) (unless due to liver metastases) * Serum creatinine \> 1.5 mg/dL. 6. Symptomatic and/or unstable pre-existing brain metastases. To be enrolled in the study, subjects must have confirmation of stable disease by MRI or computer tomography (CT) scan within 4 weeks from day 1 of cycle 1 of treatment and have central nervous system (CNS) metastases well controlled by steroids, anti - epileptics or other symptom-relieving medications. 7. Clinically relevant cardiovascular disease, i.e., myocardial infarction or other severe coronary artery diseases within the prior 6 months, cardiac arrythmia requiring medication, uncontrolled hypertension, overt cardiac failure or non compensated chronic heart disease in New York Heart Association (NYHA) class II or more. 8. History of psychiatric disabilities, potentially interfering with the capability of giving adequate informed consent. 9. Pregnant or lactating women or inability/unwillingness to practice a medically approved method of contraception during study period (including 3 months following the end of treatment) 10. Uncontrolled active infections. 11. Any condition which, in the judgement of the Investigator, would place the patient at undue risk or interfere with the results of the study.