A large number of studies have shown that patients feel more satisfied with hydromorphone in the pain management. and a systematic review found that hydromorphone may be better suited than morphine for titration of acute analgesia. However, current researches on intravenous opioid titration for cancer pain such as hydromorphone are relatively insufficient in China. Therefore, a prospective, multi-center, randomized controlled study is conducted to assess the efficacy and safety of comparing patient-controlled analgesia (PCA) versus non-PCA intravenous hydromorphone titration for severe cancer pain.

The opioid dose for individual with cancer pain to provide adequate relief of pain with an acceptable degree of side effects is variable. Opioid titration is a process to obtain the tailored dose. Conventional titration is administered by a clinician or nurse. PCA is that patients control cancer pain by self-administration of intravenous opioids using programmable pump. The aim of our study is to evaluate the efficacy of PCA titration versus conventional titration intravenously for severe cancer pain (10-point numerical rating scale, NRS ≥ 7). Injectable Hydromorphone was selected as pharmaceutical analgesics, which works as well as morphine and oxycodone and had similar side effects.

Inclusion Criteria:

1. With written informed consent signed voluntarily by patients themselves.
2. Cancer patients aged 18-70 years old.
3. Patients with cancer pain more than or equal to NRS 7 during previous 24 hours.
4. Patients who will not be treated with radiotherapy within 7 days prior to randomization and during study.
5. Patients who need chemotherapy, long term administration of hormone, targeted therapy, or bisphosphonates therapy should undergo a stable anti- tumor therapy prior to randomization.
6. Patients or his/her caregivers who are able to fill out the questionnaire forms.
7. Ability to correctly understand and cooperate with medication guidance of doctors and nurses.
8. Without a history of anaphylaxis of narcotic drugs.
9. Without psychiatric problems.
10. ECOG performance status ≤3.
11. Not participated in another drug clinical trial within one month before inclusion（including hydromorphone）.

Exclusion Criteria:

1. Patients diagnosed with non-cancer pain or unexplained pain.
2. Patients suffered with post-op pain.
3. Patients having paralytic ileus.
4. Patients who have hypersensitivity to hydromorphone.
5. There are abnormal lab results, with obvious clinical significance, such as the creatinine ≥ 2 fold of upper limit of normal value, or ALT or AST ≥ 2.5 fold of upper limit of normal value (≥ 5 fold,to the patients with liver metastasis or primary liver cancer), or liver function of Child C grade.
6. Patients having a incoercible Nausea and vomiting.
7. Monoamine oxidase inhibitor (MAOI) was administrated two week before randomization.
8. Patients who are pregnant or lactating,who plans to be pregnant within one month after the trial（including male）.
9. Patients who are opioid abuse.
10. Patients who are alcohol abuse.
11. Patients who are cognitive dysfunction.
12. Patients having a severe psychotic depression.
13. Patients with any other medical condition or reason, in that investigator's opinion, makes the patient unable to participate in a clinical trial.