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

Inclusion Criteria: * A signed informed consent document. * Male and non-pregnant, non-lactating female subjects. * Female subjects must be post menopausal, surgically sterile, or practicing an effective method of birth control and continue to do so throughout the trial. * At least 18 years of age. * Have chronic malignant tumor-related pain * Are opioid-naïve or have been pretreated with an equianalgesic dose range equivalent of up to 160 mg oral morphine per day and are dissatisfied with prior treatment. * Have a mean pain intensity of at least 5 points on an 11-point Numeric Rating Scale (where 0 indicates no pain and 10 indicates worst possible pain). * Have an expected course of the disease such that the pain that will permit compliance with the trial protocol over the entire trial period. Exclusion Criteria: * Have a life-long history of seizure disorder or epilepsy. * Have had any of the following within one year: mild/moderate traumatic brain injury, stroke, and transient ischemic attack. * Have had severe traumatic brain injury within 15 years (consisting of ≥ 1 of the following: brain contusion, intracranial hematoma, and either unconsciousness or post-traumatic amnesia lasting for more than 24 hours) or residual sequelae suggesting transient changes in consciousness. * Have a known history and/or presence of cerebral metastases. * Have moderately or severely impaired hepatic function. * Have laboratory values reflecting inadequate hepatic function. * Have thrombopenia, leucopenia or hypercalcemia * Have severely impaired renal function. * Having uncontrolled hypertension * Having clinically relevant history of hypersensitivity, allergy or contraindications to morphine or any of the excipients. * Have chronic hepatitis B or hepatitis C, or Human Immunodeficiency Virus (HIV). * Subjects currently undergoing the following concomitant therapy: radiotherapy, pain inducing chemotherapy, anti-parkinsonian drugs, neuroleptics, monoamine oxidase inhibitors, serotonin norepinephrine re-uptake inhibitors (SNRI) or any other analgesic therapy than investigational medication or rescue medication during the trial. Selective serotonin re-uptake inhibitor (SSRI) treatments are allowed if taken for at least 30 days before the screening period of the trial at an unchanged dose.