The purpose of this study is to evaluate the conversion rate based on the number of participants achieving pain control and safety within 1 week after switching the opioid (morphine-like medications) analgesics (drug used to control pain), when tapentadol extended-release (ER) (JNS024ER) is orally administered to participants treated with around-the-clock opioid analgesics, for their moderate to severe (very serious, life threatening) chronic (lasting a long time) malignant (cancerous) tumor-related (a mass in a specific area) cancer (abnormal tissue that grows and spreads in the body) pain.

This is a randomized (study drug assigned by chance), open-label (a medical research study in which participants and researchers are told which treatments the participants are receiving, "unblinded"), parallel-arm (participants receive 1 of 2 possible interventions during the same time frame throughout the study), optimal dose-titration, multicenter (when more than one hospital or medical school team work on a medical research study) study evaluating the conversion rate based on the number of participants achieving pain control and safety within 1 week after switching from an ongoing around-the-clock opioid analgesic (morphine sustained-release [SR], oxycodone controlled-release, or fentanyl transdermal) to tapentadol ER or morphine SR, for their moderate to severe chronic, malignant tumor-related cancer pain. The study consists of 2 periods: 1 to 2 week screening period, followed by 8-week open-label treatment period. During the study period, participants will be hospitalized or outpatient. However, it is preferable to be hospitalized 1 week before and 1 week after to evaluate efficacy before and after switching opioids for securing participants' safety. At Day 1, participants will receive either tapentadol ER or morphine SR twice daily. During the treatment period, the dose of the study drug will be titrated to the participant's optimal dose. The participants will receive either tapentadol ER or morphine SR twice daily for 8 weeks. The maximum dose allowed for tapentadol ER will be 500 milligram (mg) daily or morphine SR 140 mg daily throughout the study. Efficacy is primarily evaluated using pain intensity score on an 11 point Numerical Rating Scale (an 11-point NRS is used to measure the pain level where 0=no pain to 10=pain as bad as you can imagine). Participants' safety will also be monitored.

Inclusion Criteria:

• Participants with documented clinical diagnosis (determination of the cause of a medical problem) of any type of cancer (abnormal tissue that grows and spreads in the body)
• Participants with mean 24-hour Numerical Rating Scale (NRS) score (11-point NRS used to measure the pain level for the past 24-hours where 0=no pain to 10=pain as bad as you can imagine) during 3 days (Day -4 to Day -2) before randomization (study drug assigned by chance) less than 4.0
• Women must be post-menopausal, surgically sterile, or before entry and throughout the study practicing an effective method of birth control
• Participants using immediate-release (IR) morphine hydrochloride (HCl) or oxycodone HCl hydrate as rescue medication (rescue medications are medicines that may be administered to the participants when the efficacy of the study drug is not satisfactory, or the effect of the study drug is too great and is likely to cause a hazard to the participant, or to manage an emergency situation) for breakthrough pain
• Participants treated with around-the-clock opioid (morphine-like medications) therapy for moderate to severe (very serious, life threatening) chronic (lasting a long time), malignant (cancerous) tumor-related (a mass in a specific area) cancer (abnormal tissue that grows and spreads in the body) pain using one of the following opioid analgesics (drug used to control pain) before randomization: morphine SR tablet less than or equal to 120 milligram (mg) per day, oxycodone hydrochloride controlled release (CR) tablet: 15 mg to 80 mg per day, durotep MT (fentanyl transdermal [through the skin] matrix) patch less than or equal to 8.4 mg per patch, fentos tape less than or equal to 4 mg per tape, or oneduro patch less than or equal to 3.4 mg per patch

Exclusion Criteria:

• Participants with complicated uncontrolled/clinically significant arrhythmia (uneven heart beat)
• Participants who had received rescue doses 3 times or more daily within 3 days (Day -4 to Day -2) before the randomization
• History of surgery intended for the cure of the primary disease or for the treatment of cancer pain within 28 days before screening
• Participants who had application of radiotherapy (treatment of cancer using x-rays), nerve block, or stimulation analgesia within 7 days before screening
• Participants with known allergies (over sensitivity to a substance), hypersensitivity, or intolerance to opioid analgesics or its excipients