A Study to Evaluate Tapentadol (CG5503) in the Treatment of Chronic Tumor-Related Pain Compared With Placebo and Morphine

Inclusion Criteria * Male and non-pregnant, non-lactating female subjects. * Of at least 18 years of age with chronic malignant tumor-related pain with a mean pain intensity (NRS) of 5 points or higher. * Subjects who are opioid-naïve or pretreated with an equianalgesic dose range equivalent of up to 160 mg oral morphine per day and are dissatisfied with prior treatment. * Women must be postmenopausal, surgically sterile, or practicing or agree to practice an effective method of birth control throughout the trial. * Expected course of the disease and the pain that would permit compliance with the trial protocol over the entire trial period. Exclusion Criteria Key Exclusion Criteria: * Subjects will be excluded from the study if they have a history of seizure disorder or epilepsy; * known history and/or presence of cerebral tumor or cerebral metastases. * history of alcohol or drug abuse; * uncontrolled hypertension, * clinical laboratory values reflecting severe renal insufficiency, * moderate or severe hepatic impairment, * hepatitis B or C, HIV, * inadequate bone marrow reserve * currently treated with radiotherapy, * pain-inducing chemotherapy, * anti-parkinsonian drugs, neuroleptics, monoamine oxidase inhibitors, serotonin norepinephrine reuptake inhibitor (SNRI) or any other analgesic therapy than investigational medication or rescue medication during the trial. * selective serotonin reuptake inhibitor (SSRI) treatments are allowed if taken for at least 30 days before the screening period of the study at an unchanged dose.